Physiology LT
Adrenergic receptors
epinephrine and norepinephrine
What do motor neurons do
carry signals from the spinal cord to the muscles to produce movement
primary motor cortex
the section of the frontal lobe responsible for voluntary movement
What is the cardiac cycle
cardiac cycle refers to the events that occur from the beginning of one cardiac contraction (heartbeat) to the beginning of the next
Function of the corticobulbar tract
carries motor information from the cerebral cortex to the medulla oblongata
Function of the corticospinal tract
carries motor information from the cerebral cortex to the spinal cord
Hyperthermia
Abnormally high body temperature
What is mild hypothermia?
Mild hypothermia is also known as heat exhaustion
Ramus
branch
somatosensory cortex
sensations that can occur anywhere in the body
What are the 4 main plexuses?
-cervical -brachail -lumbar -sacral
How many lobes can each hemisphere be divided into?
-frontal lobe -parietal lobe -occipital lobe -temporal lobe
What parts is the brainstem made up of?
-midbrain -pons -medulla oblongata
What does the diencephalon consist of?
-thalamus -subthalamus -epithalamus -hypothalamus
Temporal lobe
A region of the cerebral cortex responsible for hearing and language.
Occipital lobe
A region of the cerebral cortex that processes visual information
Metabolism
All of the chemical reactions that occur within an organism
cortiscospinal tract
Begins in the cortex in the spine
Hair in heat conservation
Body hair keeps us warmer by trapping pockets of insulating air, so that heat is less likely to be lost to the environment. As with goose bumps, this is not an effective method of gaining or retaining heat in humans.
What are heart sounds caused by?
Caused by the closure of heart valves
Where does the spinal cord end and begin?
Extends from the medulla in the brainstem to the lower spine
Subcutaneous fat
Fat is a good heat insulator, which means it conducts heat poorly. When the environment is cold, fat provides a layer of insulation to retain body heat.
Pyrexia
Fever
Difference between heat and temperature?
Heath is a form of energy and temperature is a quantitive measurement
Hypothermia
Hypothermia is an abnormally low body temperature
Body temperatures for fever and hyperthermia often overlap (for example, > 38.8°C [100.9°F]). What makes these two temperature disturbances different?
In fever, the body's hypothalamic set point is reset
Synapse
Junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. A junction between two nerve cells signals sent to one another by chemical transmission.
Hypothalamus
Lies below the thalamus, it is both a nervous and an endocrine organ with numerous functions that mostly facililtate the maintenance of homeostasis. There are 7 main hypothalamic functions: -Autonomic control center -Center for emotional response -Regulation of body temperature -Regulation of food intake -Regulation of water balance and thirst -Regulation of sleep-wake cycles -Control of endocrine system functioning
Plexus
Network of intersecting afferent and efferent nerves. Plexuses are formed from ventral rami.
Why do we need to keep our core temperature relatively constant but not our surface temperature?
Our core contains vital organs that must remain within a narrow temperature range to function properly. The periphery of our bodies contain less vital organs, so peripheral temperatures can fluctuate within greater range without adverse affect to our bodies as a whole. Variation in our surface temperature is important because it allows our bodies to detect environmental changes early, and signal the appropriate response to maintain our core temperature.
What do pyrogens produce that causes fever
Prostaglandin E2 which causes the hypothalamus (the body's thermostat) to reset to a higher temperature
Spinal cord
Relays information from the body to the brain
Cerebral hemispheres
Responsible for processing and memory
Blood vessels in heat conservation
Skin blood vessels vasoconstrict to conserve heat in cold environments.
Pyrogens
Substances that can induce fever. They may be released into the bloodstream by invading cells or by the body's own immune system
How are eccrine sweat glands involved in heat loss?
Sweat glands deliver a hypotonic solution to the skin's surface. The process of vaporization removes heat from the body.
Function of the cerebellum
The cerebellum controls the rate, range, and direction of movement. To do this, it processes information received from other brain areas: -vestibular information -visual information -somatosensory information -motor information
What is the hypothalamic set point?
The critical temperature set-point in the hypothalamus above which sweating begins and below which shivering begins is determined mainly by the degree of activity of the heat temperature receptors in the anterior hypothalamic-preoptic area.
Dorsal rami
The dorsal rami carry motor and sensory information to and from the posterior muscles and skin.
Arrector pilli muscle in heat conservation
This muscle is activated to contract in response to cold temperature stimuli, which produces "goose bumps". Contraction of the muscle pulls on hair follicles to create a small depression on the skin's surface so the surrounding area protrudes.
What is body temperature regulated by?
The hypothalamus. The hypothalamus can be thought of as the thermostat of the body, and receives input from peripheral and central thermoreceptors. This region of the brain constantly monitors temperature conditions and signals appropriate changes in order to maintain our internal core temperature.
The mitral valve snaps shut when?
The mitral valve snaps shut when ventricular pressure exceeds atrial pressure. This prevents back flow of blood back into the atria
Occipital lobe
The occipital lobe is where the visual cortex is located. It is divided into several visual areas. The primary visual cortex contains a well defined map of visual information received from the outside world. What symptoms would you see in someone whose occipital lobe has been damaged?
The motor area in one hemisphere controls movements on which side of the body?
The opposite side. Nerves which carry motor information to the body cross over in the medulla oblongata (lower part of the brainstem) before they reach the spinal cord. Hence, the motor area in one hemisphere controls movements on the opposite side of the body.
Parietal lobe
The parietal lobe is where the somatosensory cortex is located. It integrates a variety of sensory information including auditory, visual, somatosensory, and proprioceptive information.
Frontal lobe
The primary motor cortex is located at the posterior border of the frontal lobes. It generates the nerve impulses that initiate movements. The premotor cortex is thought to be involved in planning these movements.
Temporal lobe
The temporal lobe is where the auditory cortex is located. It receives and processes auditory information. Wernicke's area is involved in understanding language.
thalamic nuclei
The thalamic nuclei are clusters of cells involved in relaying sensory and motor signals to the cerebral cortex. Every sensory system (except the olfactory system) includes a thalamic nucleus in the pathway between the receptor and the associated primary cortical area. Signals from the cerebellum and the basal ganglia are relayed through thalamic nuclei.
Ventral rami
The ventral rami carry motor and sensory information to and from the anterior muscles and skin.
Free nerve endings (thermoreceptors) in heat conservation
Thermoreceptors in the skin sense changes in the external temperature and signal the change to the hypothalamus. The hypothalamus integrates this information with all the other information about body temperature that it is receiving (for example, core blood temperature), then stimulates various structures to initiate an appropriate response to increase or decrease body temperature.
How are free nerve endings (thermoreceptors) involved in heat loss?
Thermoreceptors in the skin sense changes in the external temperature and signal the change to the hypothalamus. The hypothalamus integrates this information with all the other information about body temperature that it is receiving (for example, core blood temperature), then stimulates various structures to initiate an appropriate response to increase or decrease body temperature.
Summarize the body's response to a drop in temperature. Describe the thermoregulatory feedback loop
Thermoreceptors sense a decrease in environmental temperature and send a message to the hypothalamus, the temperature control centre of the brain. This centre is also monitoring other things including core body temperature through the temperature of the blood perfusing the hypothalamus. When temperature drops, the brain triggers a variety of voluntary behavioural responses (the urge to increase skeletal muscle movement, add layers of clothing etc). If these are not sufficient to warm us, the hypothalamus stimulates involuntary responses, the skeletal muscles will shiver giving heat. Surface arterioles constrict and the vascular shunts relax, which reduces the amount of blood flow (and heat loss) at the skin's surface and causes a pale appearance. Body hair will stand erect (goosebumps) as the arrector pili muscles (which are attached to our hair follicles) are stimulated to contract. In longer term situations, hormones can increase the basal metabolic rate, which produces more heat.
Ventral roots are efferent what does this mean?
They carry motor information from the CNS to the PNS
Dorsal roots are afferent what does this mean?
They carry sensory information to the CNS from the PNS
Function of the heart valves
To prevent back flow of blood
Convection
Transfer of heat that occurs when a fluid flows over a surface
How does a fever occur?
Typically, our bodies have a thermoregulatory set point around 36-37.3°C (97.3-99.1°F). However, chemicals known as pyrogens work to elevate the hypothalamic set point to a higher temperature [+]. The resetting of our body's thermostat causes us to rapidly generate heat in order to reach the new set point, which results in pyrexia (fever).
How are blood vessels involved in heat loss?
Vasodilation of surface arterioles brings more heat to the skin surface. Skin blood flow is normally significantly greater than that required to support skin metabolism; its major role is in heat loss.
Why does an action potential normally flow in only one direction along a nerve fiber?
Voltage gated Na+ channels enter a short, inactive state after they have been open (the absolute refractory period) During this period, the Na+ channels cannot be reactivated by local currents. It is this that prevents action potentials from flowing backwards along nerve fibres in the body
Cerebellum
What is the function of the cerebellum? The cerebellum is important for smooth, coordinated, and precise movements. It receives a huge amount of sensory input and fine-tunes motor activity accordingly.
How do sweat glands contribute to thermoregulation?
When the body detects an increase in internal temperature, the sympathetic nervous system stimulates sweat glands to produce sweat. Sweat is secreted onto the skin's surface where it evaporates and removes heat from the body
Describe the body's response to an increase in temperature
When the body temperature becomes too high, the hypothalamus triggers a range of involuntary responses to help the body lose heat. Hypothalamus stimulates the sympathetic nervous system to undergo a number of involuntary responses to cool our body temperature, including dilation of blood vessels near the surface of the skin and initiation of sweating. Vasodilation of the blood vessels allows heat to be lost via radiation across the skin's surface and the evaporation of the secreted sweat removes heat from the body
When is our body's metabolic rate at a minimum?
When the core temperature is within the thermo-neutral zone
What intergumentary structures are involved in heat conservation?
arrector pilli muscle, blood vessel, hair, free nerve endings (thermoreceptors), subcutaneous fat
What integumentary structures are involved in heat loss?
blood vessels, eccrine sweat glands, free nerve endings (thermoreceptors),
What are the major regions of the brain?
cerebral hemispheres, cerebellum, Diencephalon, Brainstem, Spinal cord
What does the characteristic 'dub' sound indicate?
closing of the aortic and pulmonary valves
What does the characteristic 'lub' heart sound indicate?
closing of the mitral and tricuspid valves
ganglia
clusters of cell bodies that lie outside of the CNS. Some ganglia contain interneurons and can act as small integrating centres
Medulla
coughing and sneezing cardiac function
which event of the cardiac cycle occurs while the aortic valve is open?
ejection
Cerebellum
involved in movement, coordination and posture
Diencephalon
involved in regulation of the autonomic and endocrine system
Brainstem
involved in sensory-motor relays and vital autonomic function
During which phase of systole does the aortic valve remain closed?
isovolumetric contraction
efferent
motor
Motor or efferent division
motor nerves carry information away from the CNS to skeletal muscle fibres to bring about an appropriate response to the stimulus
efferent
motor, carrying away from centre
preganglionic neuron
neuron that integrates in the CNS and projects to an autonomic ganglion outside of the CNS
What happens physically when the hypothalamic set point is elevated
pale appearance, addition of layers, shivering, vasoconstriction
A patient has an upper motor neuron lesion due to having a stroke which has affected their left cerebral cortex. Which symptoms are they likely to exhibit?
paralysis of right arm muscles and paralysis of right facial muscles
Dorsal root ganglion
part of the dorsal root that contains the cell bodies of sensory fibres
Somatic nerve fibers running to and from the periphery are collected together into bundles called
peripheral nerves
What is the prefrontal cortex responsible for?
planning and organisation making judgements and regulating mood moderating social behaviour and decision making
Where is the cerebellum
posterior to the brain stem
Each spinal nerve divides into a dorsal and a ventral ________.
ramus
What does isovolumetric relaxation refer to?
relaxation of the ventricles when both the mitral and aortic valves are closed
What functions does the thalamus contribute to?
relaying sensory information motor activities learning memory
afferent
sensory
Two functional subdivisions of PNS
sensory (afferent) division motor (efferent) division
Sensory or afferent division
sensory nerves carry information towards the CNS (brain or spinal cord) in response to stimulation such as pain, pressure or stretch
afferent
sensory, conveying towards the centre
Pons functions
sleep, facial expression
Thalamus
superior portion of the diencephalon, it is the relay station for sensory information ascending to the cerebral cortex
postganglionic neuron
that has an autonomic ganglion and its ganglion and its axon projects to the target tissue
What do dorsal and ventral roots do?
the dorsal roots and ventral roots connect the nerve fibres from the PNS to the CNS
Corpus collosum
the large band of neural fibers connecting the two brain hemispheres and carrying messages between them
Why does the pressure generated in the left ventricle have to be greater than that generated by the right ventricle?
the left ventricle needs to generate more pressure to overcome the greater vascular resistance of the systemic circulation
What initiates motor activity in the brain
the primary motor cortex
What symptoms might you see in a person with a cerebellar lesion?
they may have difficulty performing rapid alternating movements
What is the function of the plexus?
to redistribute the nerve fibres so that each nerve that exits the plexus will consist of fibres from a number of different spinal nerves
Conduction
transfer of heat by direct contact from one object to another
The somatic nervous system is also known as the what system
voluntary
Midbrain functions (bit below the thalamus)
voluntary movement, visual and auditory reflexes
proprioception
where the body is in relation to itself and its surroundings
does the ANS have efferent and afferent neutrons?
yes
