PNS and reflex (chapter 13)
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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
- touch receptors
all mechanoreceptors are enclosed in a __________ _________ _________
connective tissue capsule
contrast "sensation" and "perception"
- sensation: awareness of stimuli
- perception: conscious interpretation of stimuli
list several stimuli that activate nociceceptors
- chemicals from damaged tissue
- extreme temperatures
- inflammatory chemicals
- excessive pressure
list and describe 3 levels of sensory integration
- Receptor level: sensory reception and transmission to the CNS
- Circuit Level: processing in ascending pathways
- Perceptual Level: 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.
- myelin sheath
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
- Cervical Plexus
- Brachial Plexus
- Lumbar Plexus
- Sacral Plexus
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.
- Axillary nerve
- Radial/medial/ulnar nerves
- functions: 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.
- Femoral Nerve
- function: 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
- tibial nerve
- Sciatic nerve
- Function: serves the buttock, lower limb, pelvic structure and perineum.
Name the 5 components of the reflex arc.
- Receptor: detects stimulus
- Sensory Neuron: transmits afferent impulses to CNS
- Integration center: within the CNS; either monosynaptic or postsynaptic path
- Motor Neuron: conducts efferent impulses from the integration centre to the effector
- 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.
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