PNS and reflex (chapter 13)
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PNS and reflex (chapter 13)
chapter 13, A&P I
A receptor which responds to light
a receptor which responds to smell, taste, changes in blood chemistry
a receptor which is sensitive to pain-causing stimuli:
extreme heat or cold
a receptor which responds to vibration and stretch
responds to stimuli outside the body
receptors are located in skin and in most sense organs
respond to stimuli arising in the viscera and blood vessels
sensitive to chemical changes, tissue stretch and temperature changes
respond to stretch in skeletal muscles, tendons joints, ligaments and CT coverings of bones and muscles
continuously inform the brain of the bodies position and movements
_______ receptors detect the general senses. _______ receptors detect the special senses.
Simple receptors are either noncapsulated or encapsulated nerve endings.
Describe nonencapsulated nerve endings.
abundant in the epithelia and CT
responds to mostly to temperature and pain
some respond to pressure-induced tissue movement
Name 3 non encapsulated dendritic endings of simple receptors
all mechanoreceptors are enclosed in a __________ _________ _________
connective tissue capsule
contrast "sensation" and "perception"
: awareness of stimuli
: conscious interpretation of stimuli
list several stimuli that activate nociceceptors
chemicals from damaged tissue
list and describe 3 levels of sensory integration
: sensory reception and transmission to the CNS
: processing in ascending pathways
: processing in cortical sensory centers
describe the role of endogenous opioids in pain suppression
to suppress pain signals within the brain
Structure of a nerve. Order the smallest unit to the largest.
Describe the role of Schwann cells in nerve fiber regeneration
Schwann cells align to form a regeneration tube
The axon regenerates and a new myelin sheath forms
Describe spinal nerves. Distinguish between spinal roots and rami.
Spinal nerves are quite short.
Spinal roots (ventral and dorsal) branch off from the spinal cord.
The root than branches off into the spinal nerve which branches into the dorsal ramus, ventral ramus.
Ventral rami for the nerve plexuses.
Name the Major plexuses
State the major peripheral nerve that arise from the cervical plexus. Describe the general functions.
Phrenic nerve - diaphragm
Accessory nerve/hypoglossal nerve -muscles and skin of head and neck
State the major peripheral nerve that arise from the brachial plexus. Name the general function of these nerves.
: innervates muscles and skin of the upper limb
State the major peripheral nerve that arise from the lumbar plexus. State the general function of these nerves.
: innervates the thigh, abdominal wall and psoas muscle.
State the major peripheral nerve that arise from the sacral plexus. State the general function of these nerves.
Common fibular nerve
: serves the buttock, lower limb, pelvic structure and perineum.
Name the 5 components of the reflex arc.
: detects stimulus
: transmits afferent impulses to CNS
: within the CNS; either monosynaptic or postsynaptic path
: conducts efferent impulses from the integration centre to the effector
: muscle or gland that responds ti efferent impulses
To smoothly coordinate skeletal muscle activities, the nervous system must receive proprioceptor input regarding:
a) length of a muscle
: input is provided by muscle spindles
b) tension in a muscle
: input is provided by tendon organs
Input information regarding the length of is muscle is collected from?
length comes from muscle spindles.
The input for the amount of tension in a muscle and its associated tendons is provided by?
tension input is from tendon organs
Describe the stretch reflex
maintains muscle tone in large postural muscles, and adjusts it reflexively
causes muscle contraction in response to increased muscle length
all stretch reflexes are ______, while all other reflexes are __________
describe the flexor reflex
initiated by a painful stimulus
ipsilateral and polysynaptic
protective function to prevent further damage
brain can override the automatic withdrawal
describe the crossed-extensor reflex
typical occurs as the same time as a flexor reflex in a lower limb to maintain body balance
ipsilateral withdrawal reflex and contralateral extensor reflex
this reflex indicates damage to the primary motor cortex or corticospinal tract. The big toe dorsiflexes and other toes fan out.