Neuro A&P Objectives

Identify the VII cranial nerves. Know the function or each nerve. Understand what physical finding you encounter if there was a lesion of each cranial nerve.

..... Oh Oh Oh to touch and feel very good velvet ah heaven .... Some Say Marry Money But My Brother Says Be Brave Marry Money I. Olfactory (Sensory): Smell II. optic (Sensory): Vision III. oculomotor (Motor): EOM EYE IV. Trochlear (Motor): Superior oblique eye muscle EYE V. Trigeminal (Both): Sensation from the face. trigeminal ganglia sensory neurons branches into three branches (VI Opthalmic, V2Maxillary, V3Mandibular) Motor: Mastication VI. Abducens (Motor): Lateral rectus eye movements. EYE VII. Facial (Both): Facial expression and receives taste from anterior ⅔ tongue and secretion of lacrimal and salivary glands VIII. Vestibulocochlear (Sensory): balance and Hearing. IX. Glossopharyngeal (Both): taste from posterior ⅔ of the tongue. Secretion of the parotid gland. X. Vagus (Both): Innervates abdominal and thoracic viscera XI. Accessory (Motor): Innervates the sternocleidomastoid and trapezius muscle. XII. Hypoglossal (Motor): Innervates the muscles of the tongue

Explain what occurs during a nerve impulse, including saltatory conduction.

1.Cell at resting membrane potential, -70 mV. [inside cell] 2.Something causes ion channels to open allowing Na+ to enter the cells. This raises the voltage inside the cells. 3.The voltage in the cells rises to threshold, -50 mV. Once threshold is achieved, voltage gated Na+ channels open. 4.Na+ rushes into the depolarizing the cells and raising the voltage to +30 mV. 5.Sodium channels close and K+ channels open, potassium exits the cell thus lowering the cell voltage. 6.K+ channels close slowly causing the cell to hyperpolarize to -90 mV. 7.Na+/K+ ATPase pumps actively pump sodium out and potassium into the cell until resting membrane potential is obtained.

From what type of cells or tissues do neuromas usually develop?

A neuroma is a growth or tumor of nerve tissue.[1] Neuromas tend to be benign (i.e. not cancerous); many nerve tumors, including those that are commonly malignant, are nowadays referred to by other terms. Neuromas can arise from different types of nervous tissue, including the nerve fibers and their myelin sheath, as in the case of genuine neoplasms (growths) like ganglioneuromas and neurinomas.

Describe the role of the autonomic nervous system, compare and contrast the sympathetic and parasympathetic nervous system.

Autonomic NS = regulates involuntary body processes, including heart rate, respiration, digestion and pupil contraction; operates automatically without conscious direction. Sympathetic = Prepares body for action and stress. Fight or Flight Short presynaptic neuron and long post. Nicotinic receptors at the pre/post synapse, ACh is neurotransmitter. Synapse occurs in a ganglia (usually the sympathetic chain ganglia). Post synaptic neurons release NE, ACh, D Parasympathetic = calms the body and helps body conserve energy. Long presynaptic neuron and short post synaptic neuron Synapse usually occurs on target organ. Nicotinic receptors on post synaptic neuron, ACh is Neurotransmitter. Post synaptic neuron releases ACh at target organ.

Explain the cauda equina? At what spinal level does it start?

Bundle of spinal nerves and spinal nerve roots, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord. Start The Cauda Equina is a bundle of spinal nerves and spinal nerve roots this is where lumbar punctures are usually accrued to get a CSF sample usually performed at L3/ L4 as the conus medullaris is surrounded by L1 in an adult and L2-L3 in a child.

Compare and contrast each division of the nervous system

Central Nervous System (CNS) - the complex of nerve tissues that controls the activities of the body. In vertebrates it comprises the brain and spinal cord. Brain - The major processing unit of the nervous system. Spinal Cord - has certain processing ability such as that of spinal locomotion and can process reflexes Peripheral Nervous System (PNS) - The part of the nervous system that consists of the nerves and ganglia on the outside of the brain and spinal cord. The main function of the PNS is to connect the central nervous system (CNS) to the limbs and organs, essentially serving as a communication relay going back and forth between the brain and the extremities. Sensory (Afferent) Division - Neurons that carry nerve impulses from sensory receptors or sense organs toward the central nervous system Motor (Efferent) Division - Neurons that carry nerve impulses away from the central nervous system toward the peripheral effector organs (mainly muscles and glands) Somatic Division - The part of the peripheral nervous system associated with skeletal muscle voluntary control of body movements. The somatic division consists of afferent nerves and efferent nerves. Autonomic Division - The part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes. Sympathetic Division - It's general action is to mobilize the body's nervous system fight-or-flight response; it is also constantly active at a basal level to maintain homeostasis. Parasympathetic Division - It is responsible for stimulation of "rest-and-digest" or "feed and breed" activities that occur when the body is at rest, especially after eating, including sexual arousal, salivation, lacrimation (tears), urination, digestion and defecation.

Identify the different lobes and structure on the brain. Understand the biological functions of each of these structures.

Cerebrum: Frontal lobe: Higher mental functions including concentration, planning, judgment, emotional expression, creativity, and inhibition Temporal Lobe: Association Area including short term memory, Equilibrium and emotion. Occipital Lobe: visual area: sight, image recognition and image perception. Parietal Lobe: Sensory Area: sensation from muscles and skin Cerebellum: Neocortex: Motor Functions: Coordination of movement, balance and equilibrium, posture. Limbic System: thalamus: Relay and processing centers for sensory information hypothalamus: Centers Controlling emotions, autonomic functions and hormone production amygdala: center for emotions, emotional behavior and Motivation hippocampus: Center for memory forming, organizing and storing. Brain Stem: midbrain: Processing of visual and auditory data, Generation of reflexive somatic motor responses, Maintenance of consciousness pons: Relays sensory information to the cerebellum and thalamus, Subconscious somatic and visceral motor centers medulla: Relays sensory information to the thalamus, Autonomic centers for regulation of visceral functions such as cardiovascular respiratory and digestive activities.

Name and describe the major forms of hearing impairment.

Conduction deafness occurs when there is impaired transmission of sound through the auditory canal to the auditory ossicles. ex. ear wax. Sensorineural deafness: occurs when there is damage to the cochlea and cochlea nerve ex: ototoxic drugs, infection and menieres disease Presbycusis: loss of high frequency hearing with age d/t the damage of hair cells closest to the oval window from loud exposure to sounds.

Name and give the function of the three types of glia cells.

Microglia = like macrophages of the CNS, they direct immune response Astrocytes = anchor neurons to blood supply, monitor/maintain hemostasis of environment around nerves, recycle neurotransmitters Oligodendrocytes = create myelin sheath in CNS (Schwann cells in PNS)

Describe the three parts of the neuron and explain the function of the dendrite and axon.

Dendrite - receive information from other neurons, conducts toward cell body Cell Body - synthesize macromolecules, integrate electrical signals Axon - conducts information away from the cell body

Name and explain the three layers of the meninges.

Dura mater = outermost layer. external fibrous membrane surrounding the brain Arachnoid mater = Middle layer. Cushions the CNS Thin avascular, fibrous layer underlying the meningeal layer of the dura d/t cerebrospinal fluid that presses the arachnoid against the dura Pia mater = Delicate membrane. Pierced by blood vessels to nourish brain A thin, Highly vascular layer that adheres to the surface of the brain and closely follows its contours.

Define or explain the following terms: epineurium, perineurium, and endoneurium.

Epineurium - around entire nerve Perineurium - around fascicle Endoneruium - around individual axon

Classify sense organs as special or general and explain the basic differences between the two groups.Sight

In medicine and anatomy, the special senses are the senses that have specialized organs devoted to them: vision (the eye) hearing and balance (the ear, which includes the auditory system and vestibular system) smell (the nose) taste (the tongue) The distinction between special and general senses is used to classify nerve fibres running to and from the central nervous system - information from special senses is carried in special somatic afferents and special visceral afferents. In contrast, the other sense, touch, is a somatic sense which does not have a specialized organ but comes from all over the body, most noticeably the skin but also the internal organs (viscera). Touch includes mechanoreception (pressure, vibration and proprioception), pain (nociception) and heat (thermoception), and such information is carried in general somatic afferents and general visceral afferents.

Discuss how a stimulus is converted into a sensation.

In physiology, a stimulus (plural stimuli) is a detectable change in the internal or external environment. The ability of anorganism or organ to respond to external stimuli is called sensitivity. When a stimulus is applied to a sensory receptor, it normally elicits or influences a reflex via stimulus transduction. These sensory receptors can receive information from outside the body, as in touch receptors found in the skin or light receptors in the eye, as well as from inside the body, as in chemoreceptors and mechanorceptors. An internal stimulus is often the first component of a homeostatic control system. External stimuli are capable of producing systemic responses throughout the body, as in the fight-or-flight response. In order for a stimulus to be detected with high probability, its level must exceed the absolute threshold; if a signal does reach threshold, the information is transmitted to the central nervous system (CNS), where it is integrated and a decision on how to react is made. Although stimuli commonly cause the body to respond, it is the CNS that finally determines whether a signal causes a reaction or not.

Explain how the blood brain barrier works.

Is a barrier between cerebral capillary blood and cerebrospinal fluid it is composed of the tight junctions between capillary endothelial cells and glial cells. Regulates osmolarity of brain tissue and CSF and thereby the intracranial pressure and volume. It also maintains a constant environment for neurons in CNS.

List the major senses.

Sight Smell Taste Hearing Touch

Name the three types of neurons classified according to the direction in which the impulse is being transmitted. Define or explain each of them.

Multipolar interneurons Medium length Dendrite → Cell Body → Medium length Axon → Axon Terminals Short/Med len Dendrite → Cell Body → Med/Long leng Axon → Axon Terminals = have all processes confined to a single small area of CNS Motor Neuron Short Dendrite → Cell Body → Axon + Nodes of Ranvier/Myelin → Axon Terminals → Muscle = end directly on muscles, glands, other neurons in PNS ganglia Sensory Neuron Receptor Cell → [peripheral branch] Axon/Myelin → Cell Body → [central branch] Axon/Myelin → Axon Terminals = directly sensitive to various stimuli or receive direct connections from nonneuronal receptor cells

Explain what occurs at a synapse, and discuss two ways that neurotransmitter activity can be terminated.

Myasthenia Gravis = autoimmune disease that results in muscle weakness -- antibodies are produced that bind to the ACh binding sites on post-synaptic neuron and prevents ACh from binding Botulinum Toxin = prevents ACh containing vesicles from binding to cell membrane in pre-synaptic -- ACh never released into synaptic cleft

Define or explain the following terms: myelin, nodes of Ranvier, and neurolemma

Myelin - spiral wrappings of Schwann cell (PNS) or oligodendrocyte (CNS) membranes around axons, interrupted periodically by nodes of Ranvier; low-capacitance insulating coating around axons, greatly increasing their conduction velocities by allowing saltatory conduction Nodes of Ranvier - Periodic gaps in the sheaths of myelinated axons where voltage-gated Na+ channels are concentrated and action potentials are regenerated Neurolemma - outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. Forms the outermost layer of the nerve fiber in the PNS.

Explain how myelin affects neurotransmitter action potential propagation. Explain the effects of multiple sclerosis on this process

Myelin is a fatty material that coats, protects, and insulates nerves, enabling them to quickly conduct impulses between the brain and different parts of the body. Myelin coats the nerves of both the CNS and PNS. Spaces between the sections of myelin are called nodes of Ranvier. As the brain sends messages through the nerves of the spinal cord, the impulses jump from node to node. Myelin prevents these impulses from escaping from the nerve at the wrong point. Myelin also contains proteins that can be targeted by the immune system. In multiple sclerosis, T cells from the body's own immune system attack and destroy the myelin sheath, leaving the nerve cell fibers unprotected. The nerves are not as able to pass messages from the brain to the other body parts, or they are delayed or distorted, and the messages the brain receives may be misinterpreted. Myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also called plaques. These plaques can be identified by (MRI), a technique that helps assess and monitor the progression of multiple sclerosis.

Discuss the chemical receptors and their functions.

Slide 48 from lecture

Explain the function of cerebral spinal fluid, where it is produced, and the flow of CSF.

Produced by choroid plexuses. Cushions or buffers cortex of brain. Provides mechanical and immunological protection of brain. Circulates within the ventricular system. Majority of CSF is produced from within the 2 lateral ventricles, then passes through interventricular foramina to the third ventricle then the cerebral aqueduct to the fourth ventricle. From the fourth ventricle, the CSF passes through three openings to enter the subarachnoid space.

Describe the structure of the eye and the functions of its components

Rods sense light, Cones sense color Images are inverted as they pass through the lens The nerves run along the surface of the retina.

Discuss the anatomy of the ear and its sensory function in hearing and equilibrium.

The cochlea: process sound and transmit information to the brain. Hair cells that are the receptors to sound waves are located within the cochlea Semi Circular Canals: contains endolymph when rotating the endolymph shifts within the canal which allows individuals to sense which plane our head is rotating along and also the strength of the rotation. Otolithic Organs: utricle and saccule: detect linear acceleration and head positioning crystals attached to hair cells (respond to gravity) when pulled an action potential is triggered. Pinna receives the sound waves and are funneled into the auditory canal → Auditory canal external auditory meatus to the eardrum/ tympanic membrane → vibrates back and forth causing the malleus, incus, and stapes to vibrate back and forth. → stapes is attached to the oval window which begins to vibrate→ cochlea fluid movement→ circular window causes the round window to be pushed out until the energy of the sound wave is dissipated transmits electrical impulse via auditory nerve to the brain.

List and describe the functions of the spinal cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord together make up the central nervous system(CNS). The spinal cord begins at the occipital bone and extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column. Function: primarily in the transmission of neural signals between the brain and the rest of the body but also contains neural circuits that can independently control numerous reflexes and central pattern generators. 3 three major functions: as a conduit for motor information, which travels down the spinal cord as a conduit for sensory information in the reverse direction as a center for coordinating certain reflexes.

Discuss the general sense organs and their functions

Touch is a general somatic sense which does not have a specialized organ but comes from all over the body, most noticeably the skin but also the internal organs (viscera). Touch includes mechanoreception (pressure, vibration and proprioception), pain (nociception) and heat (thermoception), and such information is carried in general somatic afferents and general visceral afferents.