Kinesiology - Physiology: Neuromuscular system

central nervous system

doesn’t heal itself well

brain

complex bundle of nerves

• found in the cranium & is the control center of the body

parts of brain - cortex

centre of memory emotion & problem solving, vision, auditory, sensory & motor commands

parts of brain - brain stem

primitive part of brain controlling basic body functions like breathing, heart rate, digestion, sexual response, constriction, & vasodilation

vasodilation

enhance/ restriction of blood flow

parts of brain - cerebellum

“mini” brain that controls balance & visual acuity

spinal cord

large bundle of nerves that travel down through the spinal column

peripheral nervous system

everything found outside the CNS & is a pathway of nerves extending to & from all parts of body & carries messages both to & from the CNS

sensory pathway

carries information about the environment from various sensory receptors to the brain

motor pathway

carries command information to organs in the body to respond to stimuli from the environmentand initiates voluntary and involuntary movements.

somatic motor pathway

voluntary/conscious control such as muscle contractions

autonomic motor pathway

involuntary/unconscious control such as digestion and heart beat

sympathetic autonomic motor pathway

“fight or flight” where there is a rapid and strong response

• elevated heartrate & breathing

• pupil dilation

• suppresses non fight or flight responses

parasympathetic autonomic motor pathway

“right and digest” where it is a slow response of going back to normal

• heartrate and breathing depression back to normal

• pupil constriction

• blood flow to digestive tract

neuron

high specialized that control signals throughout the body, transmitting information between the brain, spinal cord, and muscles.

dendrite

receives incoming signals from sensory organs/other nerve cells

cell body and nucleus

organelles

Schwann cell

a type of glial cell that produces myelin sheath around peripheral nerves, facilitating faster signal transmission.

myelin sheath

protects and insulates from electrical messages from other nerve cellsnod

node de ranvier

gaps that help speed up rate at which a message travelsa

axon

along fibre that’s often covered with myelin

axon terminal or hillock

the end of the neuron

nerve functions

Na+ are actively pumped out of the cell while the K+ is pumped into the cell and is allowed to slowly leak out (3 in - 2 out rule)

• results in immediate outside of the cell to be more positive than the inside of the cell which results with a potential differences across the membrane of -70mv at restac

action potential

sequence of events that result in electrical messages traveling length of the axon starting from the cell body

• embedded in axon membrane are many proteins serving as channels for passing of materials

action potential sequence

depolarization

• protein channels closest to cell body open up & allow Na+ to flood into the cell

• once the Na+ concentration it too high, the channels will close

• K+ channels open and allow K to flow out of the cell

repolarization

• K+ channels close

• Na+/K+ pump restores the resting potential

• each sequence of depolarization/repolarization/restoration in a region initiates the same sequences adjacent region further along the axon

propagation

impulse traveling length of the axon from the cell body until it reaches the axon hillocka

all or none principle

• action potential begins when the stimulus is received by a sensory organ or when dendrites of a neuron are stimulated by impulse from another nerve

• every nerve cell has a threshold value of stimulus intensity that will trigger an action potential

• if stimulus is strong enough - action potential generates

• if stimulus isn’t strong enough - action potential won’t generate

intensity

some stimuli are seen as more intense than others but what the case it that when a stimulus generates a response in a nerve cell, it generates continuous stream of action potentials until the stimulus becomes lower than the threshold

• for more intense stimuli, the amplitude of the action potential is the same but the frequency increases

myeline and propagation rate

in a myelinated axon, ions or impulse “jumps” from node to node getting ahead of the impulse along with the axon membrane making it faster

synapse

the junction between the nerve cells

• axon from a presynaptic nerve ‘contacts’ a dendrite from a postsynaptic nerve

synaptic cleft

gap between hillock of presynaptic & dendrite of postsynaptic nerve

neurotransmitters

special biochemicals that are released by the hillock of presynaptic nerve and flood the synaptic cleft

• receptor sites on the dendrites bind to the neurotransmitters & corresponding action takes place in the postsynaptic nerve

excititory

initiate or intensify

inhibitory

stop or deescalate