ex phys test 3

chapters 3 and 4

afferent nervous division

receive sensory info from the body and moves it to the CNS

efferent nervous division

move motor info from CNS to rest of body

central nervous system vs peripheral nervous system

CNS - include brain and spinal cord

PNS - include efferent (motor) and afferent (sensory) divisions

neuron and its parts

• cell body (soma) - contain axon hillock (where axon connects) which does summation

• dendrites - receive incoming impulses

• axon - sends out signals

  • axon terminals

  • synaptic knob - contains vesicles with neurotransmitters

  • neurotransmitters - acetylcholine (cholinergic) and norepinephrine (adrenergic) are examples

synapse regions

• presynaptic terminals

• synaptic cleft

• postsynaptic receptors

myelination/myelin

• many layers of cell membrane

• in most neurons

• oligodendrocytes - myelinating cell in CNS

• Schwann cells - myelinating cell in PNS

• nodes of Ranvier - spaces between myelin involved in saltatory conduction which speeds up impulses moving down axon (make them move 50-150x faster

membrane potential

• difference in charge between inside of cell and its immediate outer surroundings

• polar - means cell is charged

resting membrane potential

• value of charge at rest

• RMP = -70 mV

  • means inside is more negative than outside

• created and maintained by:

  • 50-75X greater membrane permeability to K+ than Na+

  • Na+/K+ pump

diffusion/leak/passive channels vs Na+/K+ pump

• diffusion channels - ions move from high to low concentration

• Na+/K+ pump - these ions move from low to high concentrations which involves ATP

graded potentials (def and types)

• localized changes in MP

• 1 GP usually changes MP at axon hillock 1-2 mV

• types

  • depolarizations or excitatory postsynaptic potentials (EPSPs) - inside of cell becomes less negative

  • hyperpolarizations or inhibitory postsynaptic potentials (IPSPs) - inside of cell becomes more negative

graded potentials (cause and effect)

• caused by opening of NT-gated ion channels

• exhibit decremental spread

  • due to leak channels

• brief ion flow because NT quickly degrade

summation

• adding of incoming GPs at axon hillock

• threshold - minimum amount of stimulation required to created outgoing action potential down axon

• high degree of decision making capability

types of summation

1. spatial summation - 2 or more different presynaptic neurons firing simultaneous

2. temporal summation - a single presynaptic neuron firing rapidly

purpose of IPSP

• higher degree of decision making

• provides way for one set of signals to offset another and allows finer degree of discrimination and control determining what info is acted upon

• often involved in protecting body from injury

  • decrease in IPSP during life threatening situations

• reduction in ISPS with resistance training

purpose of summation

• highly regulated decision-making capability

• many types of info coming into body at any time

• allows us to get all the inputs and decide if that piece of info needs to be acted upon in some way or discarded

action potentials

• rapid depolarization and depolarization of neuron’s membrane

• ~ 1 ms

• all APs begin as GPs

• requires stimulation equal to or above threshold potential (all or none)

threshold potential

• 55 mV

action potential events

1. depolarization - at TP activation gate of Na+ channels open, +30 mV at peak

2. repolarization - closing of Na+ inactivation gates and then opening of K+ gates

refractory periods for APs

refractory period - time during which it is impossible or more difficult to stimulate the membrane

• absolute refractory period - time during which it is impossible to restimulate membrane because Na+ gates are not yet reset

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

restoration of Na+/K+ for action potentials

• MP is now back at resting value, but some Na+ moved inside and some K+ outside of cell during AP

• restoration of normal resting ion concentrations by Na+/K+ pump

AP wave down axon

• AP is self-regenerating

• AP moves one way down axon because area of axon upstream is in absolute refractory period, preventing backward propagation

• it can only move downstream as that area is at rest

• current doesn’t dissipate due to insulation of myelin sheath

velocity of nerve impulse transmission determination

1. myelination - myelinated neurons move impulses faster

2. axon diameter - larger diameter axons move impulse faster because of less resistance to ion flow (remember FT muscle fibers have larger axon diameters)

endocrine system

• endocrine glands secrete hormones directly into bloodstream and travels until it reaches its target organ

• at target organ, hormone attaches to specific receptor

• resultan hormone-receptor complex (HRC) causes a change in target organ resulting in biological effect

steroid hormones

• derived from cholesterol

• fat soluble (lipophilic or hydrophobic)

  • carrier proteins

  • diffuse

  • intracellular receptors

• usually not stores

• slow acting, but longer lasting

• ex: cortisol, aldosterone, estrogen, testosterone

4 major parts of the brain

1. cerebrum

2. cerebellum

3. diencephalon

4. brain stem

4 lobes of the cerebrum

1. frontal

2. parietal

3. occipital

4. temporal

what is the corpus callosum

connects the left and right halves of the brain

white vs gray matter

white: myelinated, transmits signals between parts of the brain

grey: unmyelinated, processes info, memory, and thought

frontal lobe

• primary motor cortex

  • conscious control of skeletal muscle

  • cell bodies in primary motor cortex, axons form corticospinal tracts

• premotor cortex

  • memory bank for learned motor skills of repetitious or patterned nature

temporal lobe

• hippocampus

  • converts short-term memory to long-term

  • spatial navigation

  • Alzheimer’s and amnesia

• amygdala

  • memory consolidation and processing (especially emotional memory and learning)

parietal lobe

primary sensory cortex - all sensory input and interpretation flows through here

cerebral medulla

basal ganglia

• action selection

• “brake hypothesis” - apply brake to some movements and release brake on some movements depending on the action being executed

• Huntington’s and Parkinson’s diseases

• helps maintain posture and muscle tone

diencephalon

• thalamus - sensory integrator, receives all sensory input except smell and relays to primary sensory cortex

• hypothalamus - maintains homeostasis

cerebellum

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

• main regulator of posture and balance

• same side control

brain stem

• contains midbrain, pons, and medulla oblongata

• nerves cross at medulla

• origin of 10 out of 12 pairs of cranial nerves

• controls vegetative functions

brain stem - reticular activating system (RAS)

• works with all other parts of CNS to control muscle activity

• state of consciousness

• ability to direct attention

• coordinate skeletal muscle function

• maintain muscle tone

• control CV and respiratory functions

brain stem - analgesia system

• enkephalins and beta-endorphins - opiate-like neurotransmitters that act on opiate receptors to reduce pain

• endurance exercise increases levels of opiates

spinal cord

relay between PNS and brain and controls most reflexes

PNS nerve numbers

43 pairs of nerves includes 12 pairs of cranial nerves and 31 pairs of spinal nerves

spinal cord cross section

• sensory neurons enter dorsal root

• motor neurons eneter ventral root

5 types of sensory receptors

1. mechanoreceptors - mechanical stimuli

2. thermoreceptors - temperature stimuli

3. nociceptors - pain stimuli

4. photoreceptors - light stimuli

5. chemoreceptors - chemical stimuli

specific sensory receptors

• free nerve endings

  • abundant in skin

  • touch, pressure, pain, heat/cold

  • important in preventing injury

  • initially strong stimulated, but then adapt

• joint kinesthetic receptors

  • in joint capsules

  • sensitive to joint angles and rates of change

• pacinian corpuscles

  • in tissues around joints

  • detect rate of rotation

autonomic nervous system

• controls involuntary functions, maintains homeostasis

• 2 divisions

  • sympathetic - fight or flight, uses norepinephrine

  • parasympathetic - rest and digest, uses acetylcholine

sensory motor integration

1. sensory stimulus received by sensory receptors

2. sensory AP transmitted along sensory neurons to CNS

3. CNS interprets incoming info and decides which response is most appropriate, or reflexively initiates and motor response

4. APs for response transmitted from CNS along alpha-motor neurons

5. motor AP transmitted to a muscle, response occurs

integration center

part of CNS where sensory impulse terminates, is interpreted, and linked to motor system

reflexes

• preprogrammed responses

• withdrawal reflex, reciprocal inhibition, crossed extensor reflex

muscle spindles

• sense muscle length and rate of change of muscle length

• stretch reflex (myotactic reflex)

  • rapid stretch of muscle results in reflex contraction

  • most dramatic in extensor muscle of limbs

  • protects against muscle tearing due to stretch

Golgi tendon organs (GTOs)

• monitor tension produced by muscle contraction

• inverse stretch reflex (inverse myotactic reflex)

  • senses tension on tendon, causes inhibition of agonist muscle (and stimulation of antagonist)

  • protects tendon from tearing

• decreased GTO sensitivity with resistance training

muscle chemoreceptors

• sensitive to changes in H+, CO2, and K+

• provides CNS with info about metabolic rate and muscular activity

• important in regulation of CV and pulmonary responses

innervation ratio

• number of muscle fibers supplied by a single motor neuron

• fine control - low innervation ratio

• gross control - high innervation ratio