OSSF Exam 3: The Brain and Autonomic Nervous System

Important of Brainstem Nuclei in the Regulation of ANS

Brainstem respiratory and cardiovascular centers are located in caudal medulla and pons (mostly the medulla) These regions contain upper motor neurons that regulate the function of both alpha motor neurons going to respiratory muscles and autonomic neurons that innervate cardiac and vascular smooth muscle The brainstem also contains nuclei that regulate micturition as well as chemoreceptors that are sensitive to CO2 in the CSF as well as respiratory neurons that provide respiratory drive The regulation of blood pressure is an excellent example of how afferent inputs, together with central regulation, coordinate the response of the ANS

Dicencephalon: Hypothalamus (consists of numerous....has a leaky.....allowing for.......sends signals to....allowing for....)

Consists of numerous nuclei that work to maintain homeostasis by regulating both endocrine systems via projections to the pituitary and via projections to the autonomic nervous system has a leaky blood-brain barrier, allows for the detection of lots of circulating hormones, that can activate different nuclei in the hypothalamus and send signals to the pituitary gland, which allows for the release of different hormones

Parasympathetic Nervous System: What it does?

Controls autonomic functions in the resting, unstressed animal

Major Motor Pathways: the two big ones?

brain stem pathways cortical pathways

Part of the Cerebum that contains motor cortex? Upper motor neurons send directions down to lower motor neurons to tell which muscles need to be moved/contracted. Short-term memory?

frontal lobe?

Together with the Pons, the medulla oblongata.... (is an important....)

is an imporatant realy site for auditory and vestibular information, gustatory sensations and associated motor reactions, and information about various visceral states

Basal Ganglia (Basal Nuclei) (key structure...these structures...imporant region for...)

key structures in motor planning these structures receive input from other brain regions and coordinate motor responses based on motivation, emotion, and prior learning important region for motor learning

Parts of the Brain Stem (3 parts)

medulla oblongata pons mesencephalon (midbrain)

Part of cerebrum that contains visual cortex? Processes visual information.

occipital lobe?

Part of cerebrum that contains somatosensory cortex? anythign that is happenign at the level of the body, goes though here.

parietal lobe?

Comparative Expression of Key Sensory and Motor areas (primary cortical....increased size of.....)

primary cortical regions reflect species differences increased size of "association areas" are observed with increased cognitive capacity

Part of cerebrum that contains auditory contex?

temporal lobe?

Limbic System

•Functionally and anatomically interconnected nuclei and cortical structures •Strongly associated with control of the species-survival-related behavior (e.g. reproduction, territorial aggression) •Evolutionarily highly conserved •Often considered the "feeling and reacting brain" •Linked with the autonomic nervous system

The 4 types of Brain stem pathways?

1. rubrospinal tract 2. vestibulospinal tract 3. reticulospinal tracts .4. tectospinal tracts

Posture it maitained by 3 important what? They work together to do what?

3 important brain-stem reflexes they work together to stabilize the position of the head and keep the body upright

The pons and medullar, along with cerebellum are often refered to as the?

Hindbrain

Sympathetic Nervous System: What it does?

Involved in autonomic response to stressful external stimuli

Brain Stem Pathway: Tectospinal Tracts:

Originate in the tectum of the midbrain; orienting to visual or auditory stimuli

Brain Stem Pathway: Vestibulospinal Tracts

Originate in the vestibular nuclei; regulate posture against the forces of gravity

Sympathetic Division

Preganglionic cell bodies are located in the lateral horn of the thoracolumbar (T1-L4) subdivision Axons of preganglionic cells exit the cord, enter spinal nerves, then go to sympathetic chain (paravertebral ganglia) or to prevertebral ganglia (short preganglionic fibers) ----)Prevertebral ganglia include cervical, celiac, cranial mesenteric, and caudal -----)Some preganglionic efferents go directly to the adrenal gland Postganglionic efferents tend to be 'long' since ganglia are distant from organ being innervated

Parasympathetic Division

Preganglionic neurons in brainstem and sacral spinal cord (red) ---)CNs III, VII, IX provide autonomic supply to the head ---)Vagus nerve (CN X) innervates the thoracic and abdominal viscera ---)Neurons in the gray matter of S1-S3 innervate the pelvic viscera Postganglionic neurons are very short, usually in or near the organs being innervated (green) Consequently, the parasympathetic division has long preganglionic and short postganglionic fibers

Dicencephalon: Thalamus (relay station....)

Relay station for information from sense organs to the cortex and other brain regions any sensory information that goes to cortex, has to pass through the thalamus, and projects to lots of areas in the brain

Classification of Efferent Pathways (moto pathways)

Somatic Nervous System Autonomic Nervous System

Vestibular System and Control of Eye Movement (vestibulo-occu;ar reflex is the....vestibulo-oculor reflex involves....)

The vestibulo-ocular reflex is the involuntary movement of the eyes in response to displacement of the head. This reflex allows retinal images to remain stable while the head is moved. --) cranial nerves 3 and 6 allows for this! •Vestibulo-ocular reflex involves input from the vestibular system and coordinated activity of Cranial Nerves III and VI to move the eyes in the opposite direction of the head movement (head turns right - eyes move left; gaze remains fixed).

Cranial Nerves (how many nerves...in forebrain?...in the midbrain?....from pons and medualla?....what about the vagus (x)?)

Twelve Paris of cranial nerves two in for forebrain ( I and II) --) do not emerge from the brain stem! two from the midbrain (III and IV) (ocular motor and trochlear nerve) eight from the pons and medulla ( a few cranial nerves have autonomic functions as well!) only the vagus (X) innervates structures outside the head and neck (widely distributed to the thorax and abdomen)

Autonomic Nervous System

Two divisions of ANS --the sympathetic Nervous System and the Parasympathetic Nervous System --) are antagonistic and its a balance between them! when you lose the input or enhance activation of one side over the other, what you get is symptoms that are indicative of parasympathetic dominance or sympathetic dominance Signals are transmitted to effectors which include smooth muscle, cardiac muscle, and glands. These effects are regulated by afferent feedback as well as paracrine and endocrine factors While these effects are involuntary, some effects of the ANS can be regulated by voluntary control systems or can be influenced by non-conscious descending inputs from the central nervous system

Balance and Posture: the three brain stem reflexes involved? The efferent arc of these reflexes....what are they all coordinated with?

Vestibular Reflex Tonic Neck Reflex Righting Reflex the efferent arc of these reflexes requires the activation of specific alpha motor neurons (motor units) in the head and spinal cord to correct the posture all these are coordinated with the cerebellum!

The central portion of the pons and medulla oblongata..... (contains the reticular..)

contains the reticular formation, a network interconnected neruons associated with wakefulness and generalized sensory aurosal. the reticular formation exends through the midbrain as well

The 1 type of Cortical Pathway? where does it orginate, what does it control, and important in?

corticospinal tract Originates in the motor cortex; controls voluntary motor activity and is particularly important for the control of fine motor movements

Mesencephalon (midbrain) (dorsal portion of midbrain......the ventral portion of midbrain...)

dorsal portion of the midbrain that contains the tectum (roof) which contains the bilateral rostral and caudal colliculi The ventral portion of the midbrain is referred to as the tegmentum. Nuclei within the tegmentum are critical for the control of voluntary movement and motivated behavior

Preganglionic Synaptic Signlaing

have nicotinic receprots that are made of five diffrent subunits (unique), that can come together and from distinc receprot subtypes! they have each have diffrent binding charecterstics and what specific nicotinic receptor effect this has on the opening of sodiium ion chanels! •Acetylcholine is released and binds nicotinic Acetylcholine receptors (nAChRs) •nAChRs are ligand-gated ionotropic receptors •Binding of ACh increases cation permeability (predominantly Na+) which results in excitatory signals in the postsynaptic membrane (i.e. the postganglionic neuron) •nAChRs are assembled from different subunits •Subunit composition effects ionic and ligand binding characteristics which allows for diverse physiological functions based on which subunits are expressed. •Ganglionic nAChRs have a different subunit composition when compared to those nicotinic receptors expressed by skeletal muscle (NMJ) •There are 16 different neuronal nAChR isoforms in the CNS but only one isoform at the NMJ •This differentiation is important as it underlies the effects of different pharmacological agents on the somatic versus the autonomic nervous systems

Parasympathetic postganglionic synaptic signaling

metabotropic receptors acting through g-proteins! 5 different kinds of muscarinic receptors and they can lead to different kinds of responses! --)M1, M3, and M5 lead to excitatory --)M2 and M4 leads to inhibiton tend to be slower reactions but tend to be longer lasting and ionotrophic •Acetylcholine is released and binds muscarinic receptors •Muscarinic receptors are metabotropic meaning they are G-protein coupled receptors •G-proteins effect channels or enzymes indirectly •The type of effect depends on which muscarinic receptor subtype is present on the postsynaptic membrane, or if more than one is present, which subtype has the dominant effect •For example, the heart only expresses the M2 receptor subtype, while the intestines expresses both M2 and M3 receptor subtypes •Overall the responses are more diverse, slower, and longer-lasting

Cereberum (perception of... (5 things) and how many lobes and their names?)

perception of sensation (conscious), voluntary motor control, decision-making, learning and memory frontal lobe parietal lobe temporal lobe occipital lobe

Cerebellum: what it does (7 things), regualtes ( 4 things)

planning, adjusting, and executing movement of the body, limbs, and eyes, and correction of movements! regulates the rate, range, and force of movement, fine motor coordination of the head

Spreading Activation and Hormone in the SNS

preganglionic neruon can send axon collaterals up and down chain, one preganglionic neruon can cactivea a whoel bunch of postganliinnc neruons on the cahin post ganglionic cells can affect an effector organ •Axons of the preganglionic neurons branch as they travel up and down the paravertebral chain •A single preganglionic neuron can synapse with many postganglionic neurons up and down the sympathetic chain (i.e. spreading activation) •A group of long preganglionic neurons innervate modified postganglionic cells in the adrenal medulla (chromaffin cells) that release epinephrine (80%), norepinephrine (20%) and a small amount of dopamine into the bloodstream in response to stimulation •Epinephrine and norepinephrine mediate the release of glucagon and insulin from the pancreas which further enhances energy mobilization •Hormonal effects are widespread •Other preganglionic neurons are also activated and synapse with postganglionic neurons in prevertebral ganglion •In this manner, sympathetic activation is rapid and diffuse

Cerebellum: provides what? Helps to maintain what? Gets info from...the cerebellum does not send.....?

provides correct timing of movements helps maintain muscle tone for balance and normal posture (via its connections with the vestibular system) gets info from the vestibular system, visual information, and information from Purkinje cells and muscle spindle fibers and sends outputs back to the brain stem nuclei in the midbrain, which are important for making movements, and to the pons and the medulla --) to upper lower motor neurons and sends them to the brain stem and then to lower motor neurons the cerebellum does not send projections to lower motor neurons!!! it sends it to other upper motor nuclei that then send it to the lower motor neurons!

Caudal Colliculi of Mesencephalon (receives acoustic...)

receives acoustic information and coordinates reflexes to turn the head towards unfamiliar or unexpected sounds (auditory stimulus)

Rostal Colliculi of Mesencephalon (receives visual...)

receives visual information and plays a role in the control of eye movement, particularly during visual tracking

Autonomic Nervous System (regulates...usually does not....the system is regulated.... refered to as a ..... (pre-ganglionic...post galionic...)

regulates homeostatic bodily functions usually does so autonomously the system is regulated by inputs from the hypothalamus and brain stem referred to as a "two-neuron system ---) preganglionic neuron in spinal grey matter or brain stem nuclei --) postganglionic neuron in a peripheral ganglion lengths of preganglionic and post ganglionic are different in sympathetic in comparison to parasympathetic

What does the medulla oblongata regulate? (regulate many vital...)

regulates many vital biological functions, including heart rate, respiration, gastrointestinal functions, salvation, coughing, and sneezing

Eye movments are controlled by....

the oculomotor (III), trochlear (IV) and abducens nerves (VI)

Regualtion of Motor Output (upper motor neuron..., lower motor neruon....thalmic projections....basal nuclei...., cerebellum....only the lower motor.....)

upper motor neuorons are found in the cerebral cortex and brain stem lower motor neruosn are found in spinal cord thalmic projections to the cortex provide sensroy input basal nuclei are critical for motor planning cerebellum is critical for coordinating and smoothing movements as they are being preformed only the lower motor neruons synapse on skeletal muscles

What system gives sensory system, providing information about motion, head position, and spatial orientation? Located in? Is it always active?

vestibular system --) located in the inner ear!. Always active!

Topographical Organization of Somatosensory Cortex and Motor Cortex (size for.... for the somatosensory cortex.....for motor cortex..... the map is specific.....)

• The size of the cortical surface is based on function •For the somatosensory cortex, the greater the sensitivity of a body region, the larger the cortical representation •For the motor cortex, the greater the motor control required, the larger the cortical representation •The map is species-specific but generally organized in a similar manner

Sympathetic Effecrot Receptor Subtyeps

•Adrenergic receptors (adrenoceptors, ARs) are G protein-coupled receptors •The two main types, α- and β-adrenoceptors are classified into subtypes •Epinephrine and norepinephrine can both bind to and activate all AR subtypes but with different affinities depending on the receptor subtype •ARs located on the presynaptic adrenergic terminal are referred to as autoreceptors and activation of these receptors can alter presynaptic release •Dopamine receptors in the kidney are also G protein-coupled metabotropic receptors •At high enough concentrations, dopamine can also bind ARs

Sensory Afferents from the Viscera

•Afferent input from the viscera is not considered part of the ANS but play an important role in the regulation of the ANS •Sensory receptors can be stimulated by pressure, stretch or chemicals •These afferents can stimulate local reflex function (e.g. local pacemakers in intestinal wall) •There are visceral inputs from tongue (CNs VII, IX, X), carotid sinus (CN IX), aortic arch (CN X) as well as from the thoracic and abdominal viscera (X) ---) Cells that receive these afferent inputs then send projections to the brainstem for reflexive activation (e.g. respiration, cardiac, digestive, elimination) or to the somatosensory cortex (with a relay in the thalamus) for conscious perception •Conscious perception of the viscera is due to activation of nociceptors in the viscera

ANS Neurotransmiterres

•All of the preganglionic neurons are cholinergic (Ach) acting on nicotinic receptors (N) •Postganglionic fibers of the parasympathetic system are cholinergic (Ach) acting at muscarinic (M) receptors •Postganglionic fibers of the sympathetic system are primarily noradrenergic, acting at both norepinephrine (NE) and dopamine (DA) receptors. •One exception are cholinergic sympathetic fibers that innervate muscarinic (M) receptors on sweat glands

Preganglionic and Postganglionic Neurons

•Axon of preganglionic neuron exit via ventral root •Ventral and dorsal roots fuse to form the spinal nerve •The preganglionic axon travels to the sympathetic chain •The preganglionic neuron is myelinated and the axons of these form the white ramus •The postganglionic neurons are unmyelinated and leave the ganglion as the gray ramus which rejoins the spinal nerves

Cranial Nerve Parasympathetic Efferentss

•Cranial parasympathetic nuclei include cell bodies in the facial (VII) and glossopharyngeal (IX) nuclei (these cells are sometime referred to as the salivatory nuclei) •Parasympathetic component of the oculomotor nucleus (CNIII; Edinger-Wesphal nucleus) is the origin for oculomotor parasympathetic nerves to pupillary constrictors and the ciliary muscle for the lens (accommodation)

Sensory and Motor Pathways (input from sensory.....conscious perception......projections from the......_

•Input from sensory receptors in the skin, muscles, tendons, and joints via the dorsal root ganglia •Conscious perception of somatosensory stimulation must first synapse in the thalamus before reaching the cortex •Projections from the motor cortex or brainstem (upper motor neurons) synapse on lower motor neurons in the ventral horn of the spinal cord

Brain Stem Pathway: Reticulospinal Tracts

•Originate in the reticular formation; regulate posture against the forces of gravity (regulate different muscle groups than the vestibulospinal tracts)

Brain Stem Pathway: Rubrospinal Tracts

•Originates in the red nucleus of the midbrain; voluntary and skilled movements in non-primate mammals

Sympathetic postganglionic synaptic signaling

•Postganglionic sympathetic neurons are adrenergic, releasing norepinephrine in the peripheral nerve terminals •The adrenal medulla functions as a distant ganglion, with the chromaffin cells in the medulla serving as postganglionic neurons, but when these postganglionic cells are activated, they release more epinephrine than norepinephrine •Postganglionic neurons that have their nerve endings in the kidney release dopamine with noradrenaline •So overall the sympathetic nervous system, while largely adrenergic is more accurately considered catecholaminergic •Catecholamines cause general physiological changes that prepare the body for physical activity (the fight-or-flight response) with effects like increased heart rate, blood pressure, and blood glucose levels

ANS Predominant Tone

•Predominant tone indicates which system has a stronger influence on tissue function when the body is at rest •Understanding predominant tone can help to remember how the different divisions of the ANS regulate different organ systems and why you see different clinical signs when that tone is lost, either due to pathological or pharmacological effects

Sympathetic Innervation of Head

•Provided by the cranial cervical ganglia (CCG) •CCG provides the only sympathetic innervation of the head and neck •Both preganglionic fibers to the CCG and postganglionic fibers out of the CCG travel long distances •Innervates smooth muscle of the orbit, superior eyelid, and dilator muscle. •Activation = eyes open wide/protruding with dilated pupils (increased visual acuity) Damage can lead to Horner's Syndrome --) when there's damage to side of neck

Central control of the ANS Beyond the Brainstem

•Regulation of the ANS is also influenced by the cerebrum •These influences involves extensive interconnections between many brain regions that are important for integrating autonomic control •The paraventricular nucleus (PVN) which is located in the hypothalamus is the primary integrator of autonomic signaling. •The PVN is the only brain region that has direct influence over both sympathetic and parasympathetic outflow

Dicencephalon: The two parts?

•Thalamus •Hypothalamus

Visceral Efferents of Vagus Nerve

•The vagus nerve provides widespread parasympathetic innervation of the viscera •Allows coordination of multiple effectors working together to maintain homeostasis under basal conditions

Visceral Pain Transmission

•Visceral pain fibers travel toward the spinal cord via sympathetic nerves •At the spinal cord level this visceral nociceptive pathway follows the same route as somatic pain perception (i.e. spinothalamic tract) •Within the dorsal horn interneurons receive input from both visceral (organs) and somatic (skin, muscle, soft tissues) afferent nerves which may underlie some aspects of referred pain

Tonic Neck Reflex

•signals from muscle spindles in neck that sense the change in the position of the head relative to the trunk

Vestibular Reflex

•signals from the vestibular sense organs that provide information on the position and movement of the head

Righting Reflex

•signals from the vestibular system (mediated by it) sense acceleration relative to gravity, muscle spindles in the neck sense the position of the head and proprioceptors sense the position of the body relative to gravity, to maintain appropriate posture to land on feet --) in cats it, which lets them land on their paws