Exercise Physiology Exam 2 LeeAnn Joe

What is the CNS composed of?

brain and spinal cord

What are the 2 divisions of the PNS?

afferent and efferent

What is the CNS composed of?

brain and spinal cord

What are the 2 divisions of the PNS?

afferent and efferent

What is the afferent division of the PNS?

sensory division; information from the environment to the CNS

What is the efferent division of the PNS?

motor division; information from CNS to the rest of the body

What is the function of the somatic motor division?

controls the skeletal muscle for voluntary muscle movement.

What is the function of the autonomic motor division?

regulates internal environment through involuntary movements; homeostasis

What is the sympathetic nervous division?

division used in "fight or flight"

What is the parasympathetic nervous division?

division used mainly during sleep and resting; "rest and digest"

What are the parts of a neuron?

cell body, dendrites, axon

What is the axon hillock?

the cone-shaped region at the junction between the axon and the cell body

What are dendrites?

receives signals from other neurons; many per neuron

What is the function of the axon?

carries impulses away from the cell body

What are axon terminals?

endings where axons make synaptic contact with other nerve or effector cells

What is the function of the synaptic knob?

release neurotransmitters

Neurotransmitters

??

What is a synapse?

junction between two neurons to communicate

What is a presynaptic terminal?

axon terminal that releases neurotransmitters

What is a postsynaptic receptor?

site on a dendrite to which a neurotransmitter binds

How many directions can an impulse flow through a synapse?

one; it is unidirectional

What is myelin?

layers of fat and cell membrane that wrap around the axon

What is the primary function of myelin?

speed up the impulse

What do oligodendrocytes do?

myelinate axons in the CNS

What do Schwann cells do?

myelinate axons in the PNS

What are the nodes of Ranvier?

gaps in myelin sheath along the axon

What is saltatory conduction?

the "jumping" of an impulse between the nodes of Ranvier; much faster (50 - 150x)

What is multiple sclerosis?

autoimmune disease which causes de-myelination of axons in different areas of the nervous system; neurons eventually die

What does excitable mean?

ability to conduct and transmit and impulse

What is membrane potential?

the voltage difference across a membrane

What is the resting membrane potential?

-70mV

What two things create/maintain resting membrane potential?

1. 50-75x greater membrane permeability to K+ than Na+

2. Na+/K+ pump

What is the ratio of the Na/K pump?

3 Na+ out, 2 K+ in per ATP

What does polar mean?

carries a charge; all cells are polar

What are graded potentials?

short-lived, localized changes in membrane potential

What happens to a graded potential as it travels to the axon hillock from the initiation site on the dendrites?

it becomes weak due to decremental spread because of the leak channels on the surface of the cell body

What causes a graded potential?

the opening of neurotransmitter-gated ion channels

What is depolarization or EPSP?

when the membrane becomes less negative

What is hyperpolarization or IPSP?

when the membrane becomes more negative

What is the purpose of IPSP's?

they provide a way for one set of signals to offset another; often involved in protecting body from injury

Scenarios of formations of graded potentials:

• + ion with high concentration on outside of cell -open a channel for it, + ion moves down concentration gradient into cell -positives going in -inside becomes less negative --creates a depolarization (EPSP)

• + ion with high concentration inside cell -open a channel for it, + ion moves down concentration gradient out of cell -positives going out -inside becomes more negative --creates a hyperpolarization (IPSP)

• -ion with a high concentration outside of cell -open a channel for it, -ion moves down concentration gradient into cell -negatives going in -inside becomes more negative --creates a hyperpolarization (IPSP)

• -ion with a high concentration inside of cell -open a channels for it, -ion moves down concentration gradient outside of cell -negatives going out -inside becomes more positive --creates a depolarization (EPSP)

• must sum all GPs at axon hillock

What is threshold?

minimum level of stimulation required to trigger an action potential

What voltage is threshold?

-55 mV

What is summation?

adding up all incoming graded potentials at axon hillock

What is temporal summation?

one presynaptic neuron in rapid fire

What is spatial summation?

many presynaptic neurons firing simultaneously

Why is summation important?

so that we have discrimination as to what info we act upon and what we don't.

Why have IPSPs in addition to EPSPs?

finer degree of decision-making capability; provides a way for one set of signals to offset another set

What is action potential?

rapid depolarization and repolarization of the neuron's membrane; all ion channels involved in AP's are voltage-gated and triggered at threshold

What is depolarization?

opening of Na+ activation gates - Na+ rushes into cell, changing membrane potential to about +30 mV at peak

What is repolarization?

closing of Na+ inactivation gates and the opening of K+ gates

What is the refractory period?

time following an action potential in which it is impossible or more difficult to stimulate the membrane

What is the absolute refractory period?

time during which it is impossible to restimulate membrane because the Na+ gates are not yet reset

What is the relative refractory period?

time during which it is possible but harder to restimulate the membrane because not all of the K+ gates have closed yet (-75 to -80 mV)

What is the major significance of refractory periods?

they keep the impulse going in one direction

What system restores the normal resting ionic concentrations?

Na+/K+ pump

????

AP does not decrease in intensity as it spreads (self-regenerating; no decremental spread) due to myelin. Myelin insulates the axon from loss of charge as the signal passes down axon. Other major function of myelin is to speed the conduction of the AP. Remember, APs only occur at Axon Hillock and nodes in myelinated neurons - myelination allows for saltatory conduction.

Velocity of nerve impulse transmission is determined by what two things?

myelination and neuron diameter

What are the 4 parts of the brain?

cerebrum, cerebellum, diencephalon, brain stem

What are the 5 lobes of the cerebrum?

frontal, parietal, temporal, occipital, insula

What connects the left and right hemispheres of the brain?

corpus callosum

What is the cerebrum?

center of mind and intellect; divided into left and right hemispheres

What is the function of the prefrontal cortex?

higher level thinking, control over actions/emotions

What is the function of the primary motor cortex?

voluntary control of skeletal muscles; map of the body

What is the homunculus?

part of the primary motor cortex which contains more cortical area for fine motor skills

What form the corticospinal tracts?

axons from the cell bodies in primary motor cortex

What is the function of the premotor cortex?

learned motor skills of a repetitious or patterned nature; memory bank for skilled motor activities

What is the function of the hippocampus?

converts short term memory into long term memory; spatial navigation

Injury or degradation of the hippocampus can lead to what?

alzheimer's / amnesia

What is the function of the amygdala?

- memory consolidation and processing, especially emotional memory and learning (especially fear)

- sorting new info and short-term memory

The hippocampus and amygdala are used in what?

learning

What is the function of the primary sensory cortex?

location for all sensory input and interpretation

Basal ganglia

• Action Selection

• "brake hypothesis" -- To sit still, you must put the brakes on all movements except those that maintain posture. To move, you must apply a brake to some postural reflexes, and release the brake on voluntary movement.

• Deficits result in either the presence of extraneous unwanted movements or an absence or difficulty with intended movements

• Huntington's and Parkinson's Diseases

• Text says "initiating movements of a sustained and repetitive nature such as walking and running"

• Help maintain posture and muscle tone

What is the function of the thalamus?

sensory integrator; receives all sensory input (except smell) and relays to primary sensory cortex

What is the function of the hypothalamus?

maintains homeostasis; controls the endocrine and nervous system, body temperature, water balance (thirst), hunger various drivers and fat, carbohydrate, protein metabolism. It also controls limbic brain activities.

What is the function of the cerebellum?

- coordinates timing of motor activities, rapid progression from one movement to the next, and intensity of activity

- main regulator of posture & balance

Does the cerebellum influence the same side or the opposite side of the body?

same side

What are the 3 parts of the brain stem?

midbrain, pons, medulla oblongata

What is the function of the brain stem?

relay between spinal chord and brain; controls vegetative functions

Where do the nerves cross in the brain stem?

medulla

How many cranial nerves originate from the brain stem?

10 out of the 12 cranial nerves

What is the reticular activating system?

system that works with all the other parts of the CNS to control muscle activity

What are the functions of the reticular activating system?

- state of consciousness (arousal and sleep)

- ability to direct attention

- coordinates skeletal muscle function

- maintains muscle tone

- controls cardiovascular and respiratory functions

What is the analgesia system?

system that releases enkephalins and B-endorphins to act on opiate receptors to reduce pain

Does the level of opiates increase or decrease with increase of endurance exercise?

The dorsal root carries which impulse?

sensory input

The ventral root carries which impulse?

motor output

What are reflexes?

rapid, predictable, and involuntary responses to stimuli that primarily occur in the CNS, but not typically in higher brain

How many pairs of nerves are in the PNS?

43 pairs

How many pairs of cranial nerves are there?

12 pairs

How many pairs of spinal nerves are there?

31 pairs

What are the 5 types of sensory receptors?

mechanoreceptors, thermoreceptors, nociceptors, photoreceptors, and chemoreceptors

What are free nerve endings?

receptors that respond to touch, pressure, pain, heat, and cold; important in preventing injury; initially strongly stimulated but adapt

What are joint kinesthetic receptors?

receptors located in joint capsules that are sensitive to joint angles and rates of change

What are pacinian corpuscles?

receptors in tissues around joints that detect rate of joint rotation

What is the function of the autonomic nervous system?

controls involuntary functions to maintain homeostasis

What are the 2 divisions of the autonomic nervous system?

sympathetic and parasympathetic

What is the function of the sympathetic nervous system?

fight or flight responses (norepinephrine)

What is the function of the parasympathetic nervous system?

"rest and digest" responses; uses acetylcholine

What are the 5 steps of sensor-motor integration?

• 1. A sensory stimulus is received by sensory receptors.

• 2. The sensory AP is transmitted along sensory neurons to the CNS

• 3. The CNS interprets the incoming information and determines which response is most appropriate, or reflexively initiates a motor response

• 4. The APs for the response are transmitted from the CNS along alpha-motor neurons.

• 5. The motor AP is transmitted to a muscle, and the response occurs.

What is the integration center?

area of CNS where a sensory impulse terminates, is interpreted, and linked to the motor system

???????

Spinal cord termination -simple motor reflex

• Lower brain stem termination -subconscious motor reactions (ex. postural control)

• Cerebellum termination -subconscious control of movements, center of coordination

• Thalamus termination -begin to enter level of consciousness

• Cerebral cortex termination -discretely localized signals -constant awareness of surroundings