Ch.13 Flashcards
Sensory Receptors
- Classified by Stimulus Detected and Location
- Mechanoreceptors - pressure
- Thermoreceptors - temperature
- Photoreceptors - light
- Chemoreceptors – chemicals in solution
- Nociceptors - pain
Classified by Location
Sensory Receptors
- Exteroceptors: detect stimulus from outside body (merkel cells in skin, photoreceptors in eye, etc.)
- Interoceptors (visceroceptors): detect stimuli inside body (blood pressure, bladder filling, etc.)
- Proprioceptors: detect stretch in muscles, joints, tendons, ligaments
Receptor pathway
Stimulation detected by receptor
↓
graded potential
↓
Action potential
↓
Impulse to sensory cortex of brain
Localization and Interpretation (perception)
The frequency of the impulses
helps the cortex interpret the strength of the stimulus
Adaptation
Receptor
change in sensitivity (i.e. nerve impulse transmission) in the presence of a constant stimulus
Tonic Receptors
Receptor
sustained response with little or no adaptation (nocioceptors - pain and proprioceptors - stretch)
- Typically it is a 3 neuron path
Nerves
bundles of axons in the PNS (in the CNS they are called tracts)
Mixed Nerves
contains axons of motor and sensory neurons
Cranial Nerves
- 12 pair
- Innervate the head and neck primarily (but vagus does viscera)
- Numbered with roman numeral anterior to posterior & named
CN 1-12 Title mantra
- I (1): Olfactory - Oh
- II (2): Optic -Once
- III (3): Oculomotor - One
- IV (4): Trochlear - Takes
- V (5): Trigeminal - The
- VI (6): Abducens - Anatatomy
- VII (7): Facial - Final
- VIII (8): Vestibulocochlear - Very
- IX (9): Glossopharygeal - Good
- X (10): Vagus - Vacations
- XI (11): Accessory - Are
- XII (12): Hypoglossal - Heavenly
CN 1-12 Function Montra
- I (1): Sensory - Some
- II (2): Sensory - Say
- III (3): Motor - Marry
- IV (4): Motor- Money
- V (5): Both - But
- VI (6): Motor - My
- VII (7): Both - Brother
- VIII (8): Sensory - Says
- IX (9): Both - Big
- X (10): Both - Brains
- XI (11): Motor - Matter
- XII (12): Motor - More
CN I (1)
- Title: Oflactory
- Sensory
- Smell
CN II (2)
- Title: Optic
- Sensory
- vision
CN III (3)
- Title: Oculomotor
- Motor
- move eyeball, constrict pupil, adjust lens
CN IV (4)
- Title: Trochlear
- Motor
- move eyeball
CN 5 (V)
- Title: Trigeminal
Both: - Sensory: skin/muscles around the eyes, nose, mouth, cheeks, tongue (not taste)
- Motor: chewing muscles
CN 6 (VI)
- Title: Abducens
- Motor
- moves the eyeball
CN VII (7)
- Title: Facial
Both: - motor: facial expression & glands (tear, saliva) - - sensory: proprioception & taste
CN VIII (8)
- Title: Vestibulocochlear
- Sensory
- hearing and balance
CN IX (9)
- Title: Glossopharyngeal
Both: - sensory: taste and tongue sensation
- motor: swallowing, speech, salivating
CN X (10)
- Title: Vagus
Both: - sensory: sensations of the thorax and abdominal organs, pharynx, epiglottis
- motor: swallowing, coughing, speech, contraction of GI tract & slowing the heart rate
CN XI (11)
- Title: Accessory
- motor
- swallowing, moving the head and shoulders
CN XII (12)
- Title: Hypoglossal
- motor
- speech, swallowing
Spinal Nerves
31 pairs =
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccyx
Dorsal roots
Spinal nerves
contain sensory fibers that arise from sensory neurons in the dorsal root ganglia
Ventral roots
Spinal Nerves
Motor fibers from ventral horn motor neurons
Spinal Nerve
splits to form dorsal ramus and ventral ramus, and a small meningeal branch that reenters vertebral canal
Rami communicantes
joined to the base of the ventral rami of the thoracic spinal nerves; contain autonomic nerve fibers
Dorsal Rami
- Supply the dorsal body trunk
- Each ramus innervates a narrow strip of the skeletal muscles and skin in line with point of emergence from the spinal cord
Ventral Rami
- Thoracic primarily supply the skin and skeletal muscles of the anterolateral thorax and abdomen
- In Cervical, Brachial, Lumbar, Sacral
– ventral rami join after leaving the vertebral column to form a plexus
– in these plexus fibers cross and are redistributed
Cervical plexus
- Formed from (C1-C4)
- Innervates the skin and muscles of the neck, head and superior shoulders and chest
- Phrenic nerve = innervates diaphragm (used to breath)
Brachial Plexus
- Formed by C5-C8, T1
- innervates the skin and muscles of the shoulders, superior thorax, and upper limbs
What does brachial plexus innervate?
- Innervates Deltoid muscle and shoulder skin
- Innervates Biceps, Brachialis and skin of anterior lateral forearm
- Innervates forearm flexors and skin of anterior hand
- Innervates triceps muscle and forearm extensors and skin of posterior hand
- Innervates hand flexors and medial hand
Lumbar Plexus
- Formed from L1-L4
- Innervates the skin and muscles of the anterolateral abdomen, external genitals, and part of the lower limbs
- Femoral innervates thigh flexors and leg extensors
Sacral plexus
- Formed by L4-L5, S1-S4
- Innervates the skin and muscles of the buttock and lower limbs
- Sciatic Nerve forms the Tibial and Fibular branches to innervate thigh, leg, and foot
Motor Endings
Integration for these activities is in the spinal cord, cortex, basal nuclei and cerebellum
Innervating Skeletal Muscle
Motor Endings
Somatic motor neurons release Ach, this directly opens ion channels and muscle contracts
Innervating Smooth Muscle and Glands
Motor Endings
Autonomic motor neurons release either ACh or NE at varicosities –> indirectly causes ion channels to open and muscles to contract, glands to secrete
Reflex Activity
- rapid, predictable, involuntary, unlearned motor responses to stimuli
- protects body from harm
- important clinically
- reflexes coordinated in the brain (usually
brain stem) OR in the spinal cord - some you are aware of (somatic reflexes) because they involve skeletal muscle contraction – EX: like jerking your hand from a hot stove
OR - you may not be aware of (autonomic reflexes) - like dilation of pupils
Abnormal reflexes
indicate that the
nervous system is damaged
Patellar reflex
tap knee with hammar –> leg will extend
For skeletal muscles to perform normally:
- The Golgi tendon organs (proprioceptors) must constantly inform the brain as to the state of the muscle (gives info on tension)
- Stretch reflexes initiated by muscle spindles must maintain healthy muscle tone (gives info on length)
Muscle spindle
- Lack myofilaments
- Not contractile but receptive
Muscle Spindle Refex
- add load to muscle
- muscle and muscle spindle strech as arm drops
- reflex contraction inated by muscle spindle restores arm position
Golgli tendon relfex
- Keeps muscle from ripping off of bone
1. neuron from golgi tendon organ flies
2. MN inhibited
3. muscle relaxes
4. load released
Crossed extensor reflex
The crossed extensor reflex has two parts:
- The stimulated side is withdrawn –> Noxious stimulus: flexor reflex
- The contralateral side is extended –> Reciprocal activation: extensor muscles activated
Examples:
- Stepping on a piece of glass
- Being grabbed by someone
