Phys Exam 2 Peripheral Nervous System

What is a stimulus?

change detectable by the body

Where do afferent neurons have sensory receptors?

at their peripheral endings

What does a stimulus do to a sensory receptor?

alters receptors membrane permeability, resulting in a graded receptor potential

What determines the size if a receptor potential?

strength of the stimulus - stronger = larger

What happens when the receptor potential reaches threashold?

voltage gated Na+ channels open, Na+ enters the neuron

What kind of input do visceral / sensory afferents carry?

visceral - subconscious

sensory - conscious

What is the purpose of pain?

protection - warns you about actual or potential tissue damage

What triggers pain?

stimulation of danger-sensing nociceptors

What does pain bring to conscious awareness?

Tissue damage that is occurring or is about to occur

Why is it important to remember painful experiences?

avoid potentially harmful events in the future

What is the brains built in system to reduce pain? What chemicals are involved?

built in analgesic (pain-relieving) system, edorphins

What are nociceptors?

sensory receptors that detect potentially damaging stimuli

What does accommodation do for the eye?

increases the strength of the lens for near vision by becoming more rounded/curved

What determines the strength of a lens?

shape, controlled by ciliary muscle

What must light pass through before reaching photo receptors?

Several layers of the retina

What is the visual field?

field of view that can be seen without moving head

What structures elaborate/process the visual message?

The thalamus and visual cortex

What are the three parts of the ear?

external, middle, inner

What are sound waves?

traveling vibrations of air

What is deafness caused by?

defects in either conduction or neural processing of sound waves

What is the role of the vestibular apparatus?

important for equilibrium by detecting head position and motion

What do semicircular canals and otolith organs detect?

Semi - rotational / angular movement of head

Otolith- straight line and gravity

What are chemoreceptors?

receptors for taste and smell that generate neural signals on binding with particular chemicals in their environment

What sensations are associated with food intake?

Taste and smell

How do taste and smell affect digestion?

influence the flow of digestive juices

How do taste and smell affect appetite?

increase or decrease by producing pleasurable or objectionable sensations to seek or avoid the food

How are taste buds arranged?

Bud consists of abut 50 long spindle shaped taste receptor cells

What are the 5 kinds of taste?

salty, sour, sweet, bitter and umami

What is a part of the somatic ns?

skeletal muscle

What is a part of the autonomic ns?

smooth muscle, cardiac muscle, glands

What does the preganglionic neuron do?

goes from cns to ganglion

What does the postganglionic neuron do?

goes from the ganglion to effector organ

What are the two branches of the ANS?

sympathetic and parasympathetic

What is dual innervation?

Innervation of a single organ by both branches of the ans

What do parasympathetic postganglionic fibers release?

Acetylcholine (cholinergic)

What do sympathetic postganglionic fibers release?

Norepinephrine and epinephrine (adrenergic)

What response does the sympathetic ns have? parasympathetic?

a- fight or flight

ps- rest and digest

How are the two divisions of the ans usually controlled?

reciprocally - when one increases, the other decreases

What is the adrenal medulla? What does it release?

a modified part of the sns. releases catecholamine hormones when stimulated

What part of the brain is most directly responsible for autonomic output?

the medulla in the brain stem

What does the hypothalamus play a role in?

integrating autonomic, somatic and endocrine responses

What supplies skeletal muscles?

motor neurons that cause muscle movement

Where do motor neuron axons start and end?

CNS → skeletal muscle

What neurotransmitter do motor neurons release?

Ah- which stimulates muscle contraction

Why are motor neurons called the final common pathway?

They are the final neurons that send signals to skeletal muscles

Where do motor neurons connect with skeletal muscle?

neuron muscular junction (NMJ) - each muscle cell has one

What is a muscle fiber?

A single, long, cylindrical muscle cell

What is a terminal button?

The enlarged end of a motor neuron’s axon terminal

What is the motor end plate?

The shallow depression on the muscle where the axon terminal ends

What neurotransmitter is used at the NMJ? Where is it stored?

ACh- stored in vesicles inside the terminal buttons

What is an end-plate potential? (EEP) What does it cause?

A change in the muscle cels electrical charge caused by ach

causes a muscle action potential, which leads to contraction

What is ACh’s activity? What does it do?

Acetylcholinesterase (AChE), breaks down ACh and turns off the muscles electrical response