Mod 2 Flashcards
(33 cards)
Function and structure of the SNS
Release sweat
Contraction of arrector pilli
Dilation
Vasoconstriction
Accelerates heartbeat
Increase force of contraction
Reduce peristalsis in alimentary canal
Dilate pupils
Contract smooth muscles to open eyelids
Increase peristalsis carrying spermatozoa
Relax smooth muscle for easier breathing
Release epinephrine
Function and structure of the PSNS
Constrict pupils
Contract to relax suspensory ligaments
Tear and serous secretion flow
Decrease heartbeat
Bronchioconstriction
Respiratory, pancreas, and alimentary canal gland secretion
Alimentary canal peristalsis
Relax sphinceter muscles
Facilitates bile release
Stimulates erection
Neurotransmitters of the ANS
PSNS is primarily cholinergic.
- responds to acetylcholine
- nicotinic: PSNS and SNS
- muscarinic: PSNS
SNS is primarily adrenergic.
- respond to epinerphrine
Motor areas
Premotor cortex: postural and axial movements
Supplementary motor cortex: trunk and girdles, bilateral coordination
Fontal eye fields: coordinate eye movements
Cingulate motor areas: emotional aspects of movement
Motor areas of the cerebral cortex
The grey matter of the cerebral cortex has 6 layers of cells, each with a specific function.
- Layer V is most prominent with pyramidal cells of the UMN
Cell columns serve one specific area of the body
Path of the corticospinal tract
Axons descend:
1. corona radiata
2. internal capsule
3. midbrain
4. pons
5. most fibers decussate in the lower medulla
6. spinal cord
Will synapse on one of three cells:
1. interneurons
2. alpha motor neurons
3. gamma motor neurons
Lateral and anterior corticospinal tracts
Lateral:
- distal musculature
- damage –> UMN symptoms
Anterior:
- axial, girdle musculature
Corticonuclear tract
Terminate in head and neck
Synapses on:
- cranial nerve nuclei
- brachiomotor nuclei (skeletal mm of head and neck)
Muscle spindles
Extrafusal muscle fibers make up the bulk of the muscle and cause muscular contraction leading to movement.
- innervated by alpha motor neurons
Intrafusal muscle fibers make up the muscle spindles and provide feedback regarding muscular contraction
- innervated by gamma motor neurons and sensory fibers
UMN symptoms
Spastic
Hypertonic
Hyperreflexic
Disuse atrophy
Positive babinsky
LMN symptoms
Flaccid
Hypotonic
Hyporeflexic
Denervation atrophy
Negative babinsky
Descending motor pathways
Corticotectal and tectospinal tracts
Corticorubral, rubrobulbar, and rubrospinal tracts
Corticoreticular and reticulospinal tracts
Vestibulospinal tracts
Corticotectal and tectospinal tracts
Coordinate head and eye movements
Tectum: where the superior colliculus resides
Corticorubral, rubrobulbar, and rubrospinal tracts
Coordinate hand and digits
Red nucleus: facilitates alpha and gamma neurons
Corticoreticular and reticulospinal tracts
Coordinates posture and limb movements
Reticular system: functions in consciousness
Vestibulospinal tracts
Maintains posture and balance
Vestibular system: equilibrium
Components of spinal reflexes
Sensory receptors
Sensory nerves
Motor nerves
Skeletal muscle
Skeletal muscle receptors
Muscle spindle: within the muscle, velocity and length
Golgi tendon organ: within muscle tendon, amount of tension
Specific spinal reflexes
Muscle stretch reflex
Reciprocal inhibition
Autogenic inhibition
Flexor reflex
Crossed extension reflex
Muscle stretch reflex
Deep tendon reflex
Monosynaptic
Enhanced by reciprocal inhibition
Reciprocal inhibition
Primary mover contracts, antagonist muscle relaxes
Involved inhibitory interneuron
One muscle (e.g., the extensor) is stimulated to undergo contraction, while another muscle (e.g., the flexor, its antagonist) is simultaneously inhibited from undergoing contraction and, therefore, relaxes.
Autogenic inhibition
GTO fine tunes movement and inhibits further contraction
Sends inhibitory signal when too much tension is being placed on one muscle.
GTOs are specialized receptors that monitor the tension applied to tendons generated mainly by muscle contraction.
Muscle contraction causes the sensory endings terminating on tendons (the GTOs) to discharge.
Flexor reflex
Withdrawal reflex
Response of an entire limb to noxious stimulus resulting in flexion/ withdrawal
The flexor reflex is elicited by stimulation of cutaneous receptors and includes a reflex response across several joints involving an entire limb.
Crossed extension reflex
Maintains balance/posture
The crossed extension reflex occurs to maintain balance and upright posture following contact with a noxious stimulus.
The “crossed extension reflex” occurs in the contralateral limb that does not encounter the noxious stimulus.
