KNR 181- Exam 4

What does the PNS do? What does it include?

acts as a link between the outside world and our brain (CNS)

includes: sensory receptors, ganglia, motor endings, nerves

What is sensory division?

involves structures that respond to changes in stimuli in the environment

What can sensory receptors be classified by?

1. type of stimulus

2. body location

3. structure

What are the classifications of stimuli that can be detected? What do they mean?

mechanreceptors- respond to touch, pressure, vibration, stretch, itch, etc

thermoreceptors- temp.

photoreceptors- light (through retinas)

chemoreceptors- chemicals (heart)

nocioreceptors- pain

What are the location classification for sensory receptors?

interoceptors

externoreceptors

proprioceptors

What are interoceptors?

respond to stimuli arising within the body: chemical changes, stretching, of tissues, temp.

What are exteroreceptors?

sensitive to stimuli arising outside the body: touch, pressure, pain, temp.; receptors of special sense organs; located in skin, oral cavity, eyes, ears, nose

What are proprioceptors?

respond to internal stimuli, location is restricted to musculoskeletal organs (joints), provide the brain info to location of body in space (kinesthetic awareness)

What are simple receptors? Where are they located?

most common receptors

located in skin, mucus membrane, muscle, connective tissue

What are complex receptors?

localized collections of cells (sensor organs) that work together to accomplish a specific receptive process

examples: vision, hearing, smell, taste

What are unencapsulated endings (free nerve endings) of simple receptors?

small, knoblike swellings as distal ends; sense pain, temp., pressure, itch

What are encapsulated endings of simple receptors?

1+ fiber terminals enclosed in a connective tissue capsule, virtually all are mechanoreceptors

What do muscle spindles on encapsulated endings of single receptors detect?

muscle stretch, reflex that resists the stretch, located in muscle belly

What do golgi tendon organs (GTOs) on encapsulated endings of single receptors detect?

muscle tension, housed in tendons

What do join kinesthetic receptors on encapsulated endings of single receptors monitor?

stretch in articular capsules, info on joint position and motion

What is sensation?

awareness of the change/stimulus

What is perception?

conscious interpretation of the stimulus, determines how we'll respond to stimulus

What is adaptation?

occurs when sensory receptors are subjected to an unchanging stimulus, receptor membranes become less responsive, receptor potentials decline in frequency or stop

Where are the chains of the three neurons and where do they conduct sensory impulses?

1. first-order neurons: conduct impulses from skin to spinal cord or brain stem

2. second-order neurons: transmit impulses to thalamus or cerebellum

3. third-order neurons: located in the thalamus, conduct impulses to somatosensory cortex of the cerebrum

What happens during initial stimulation of nocioceptors?

triggers release of glutemate and substance P, second order afferent neurons are stimulated, third order neurons analyze the stimulus in the brain (thalamus)

What are cranial nerves?

12 pairs, arise from the brain

serve: sensory, motor, or both functions

identified by a number and a name

What are the 12 cranial nerves?

1. olfactory nerve

2. optic nerve

3. oculomotor nerve

4. trochlear nerve

5. trigeminal nerve

6. abducens nerve

7. facial nerve

8. vestibulocochlear nerve

9. glossopharyngeal nerve

10. vagus nerve

11. accessory nerve

12. hypoglossal nerve

What is the olfactory nerve (I)?

sensory, used for smell

What is the optic nerve (II)?

sensory, used for vision

What is the oculomotor nerve (III)?

motor, "eye mover", innervates 4 of 6 extrinsic eye muscles and the upper eyelid, provides parasympathetic supply to the iris and the lens of the eye, pupillary reflex, eye movement

What is the trochlear nerve (IV)?

motor, extrinsic eye muscle, eye movement

What is the trigeminal nerve (V)?

motor, muscles of mastication (chewing), greatest cutaneous sensory distribution of any cranial nerve, sensory, has 3 branches- 2 of which innervate the teeth, facial muscles, clenching jaw

What is the vagus nerve (X)?

motor- innervates muscles of the pharynx, palate, and larynx

sensory- taste

sensory fro receptors that monitor BP and gas levels in the blood, pharynx and larynx, thoracic and abdominal organs

only cranial nerve to extend beyond the head and neck to thorax and abdomen

Where are the 31 pairs of spinal nerves located and how many are there in each area?

8 cervical

12 thoracic

5 lumbar

5 sacral

1 coccygeal

What are the two medial roots that each spinal nerve connects to the spinal cord? Explain each one

ventral roots: arise from the anterior horn and contain motor efferent fibers

dorsal roots: arise from sensory neurons in dorsal root ganglion, contain sensory afferent fibers

True of False: each spinal nerve is very long

false- each spinal nerve is very short, about 1-2 cm

What are rami in spinal nerves? What are their subdivisions?

distal to "roots" and can have combined motor and sensory function

dorsal rami- muscles and skin near midline of the back

ventral rami (thoracic region)- intercostal nerves that supply the thorax and upper abdomen

What are plexuses?

all ventral rami (except T2-T12) form interlacing nerve networks (plexuses); found in the cervical, brachial, lumbar, and sacral regions

What is the cervical plexus?

spinal nerves C1-C4: muslces and the skin of the neck and shoulder

phrenic nerves C3-C5: diaphragm, sole motor function, "wind knocked out", spinal injury at C3-C5= respiratory arrest

What is the brachial plexus?

C5-T1, innervate the upper extremity, can be palpated just superior to the clavicle at the lateral border of the sternocleidmastoid muscle

What is the lumbar plexus?

L1-L4, mostly innercates the anterior and medial thigh

What is the sacral plexus?

L4-S4, immediately caudal to lumbar plexus

What is a dermatome?

the area of skin innervated by the cutaneous branches of a single nerve, all spinal nerves except for C1 participate in dermatomes

What is a reflex arc?

a rapid, predictable motor response to a stimulus; involve only peripheral nerves and the spinal cord, involve higher brain centers as well

may be: be inborn (intrinsic) or learned (aquired)

What does a somatic reflex activate?

skeletal muscle

What does an autonomic reflex activate?

smooth muscle, cardiac muscle, glands

What are the five components of a reflex arc?

1. receptor- site of stimulus

2. sensory neuron- transmits the afferent impulse to the CNS

3. integration center- either monosynaptic or polysynaptic region within CNS

4. motor neuron- conducts efferent impulses from the integration center to an effector

5. effector- muscle fiber or gland that responds to the efferent impulse

What are muscle spindles in stretch reflex?

rapid forceful stretching activates the spindle, causes contraction, ballistic stretching, ex: sleeping in class or patellor reflex

What is the golgi tendon organ reflex?

the opposite of the stretch reflex, contracting the muscle activates the golgi tendon organs, afferent golgi tendon neurons are stimulated-> neurons inhibit the contracting muscle-> the antagonistic muscle (muscle on opposite side) is activated, results in the contracting muscle relaxing and the antagonist contracting

What does the ANS do? What are the structures involved?

regulates activity of smooth muscle, cardiac muscle & certain glands, stability of internal environment depends largely on ANS

Structures involved:

general visceral afferent neurons, general visceral efferent neurons, integration center within the brain

What are the efferent pathways of the ANS?

uses "two neuron" chain, preganglionic neuron-> autonomic ganglion -> postganglionic neuron, light to no myelination, slower conduction

What are the efferent pathways of the SNS?

motor neuron cell bodies are in CNS, axons extend via spinal or cranial nerves to their effects (skeletal muscles), rapid conduction

What is a preganglionic neuron in the ANS?

resides in the brain or spinal cord, axon is lightly myelinated and extends to autonomic ganglion

What is a postganglionic neuron in the ANS?

cell body lies outside the CNS, axon is unmyelinated that extends to the visceral effector

What is the ANS target organs' responses to neurontransmitters?

sympathetic fibers release norepinephrine, parasympathetic fibers release ACh, can be either inhibitory or excitatory- depending on the type of receptors on the response organ

What is the SNS target organs' responses to neurotransmitters?

ACh, exitatory, facilitates contraction of skeletal muscle

What are the two major divisions of the ANS?

parasympathetic and sympathetic

Anatomically, how do the parasympathetic and sympathetic divisions differ?

their origin sites, the relative lengths of their fibers, the location of their ganglia

What are the origin sites of the parasympathetic division of the ANS?

emerge from the brain and sacral spinal cord, aka craniosacral

What are the orgin sites of the sympathetic divison of the ANS?

originate in the thoracolumbar region of the spinal cord

Where are the sources of dual innervation of the parasympathetic divison of the ANS?

preganglionic cell bodies arise from nuclei of 4 cranial nerves and the sacral spinal cord

Where are the sources of dual innervation of the sympathetic division of the ANS?

preganglionic cell bodies arise from thoracic and first 2 lumbar segments of spinal cord

What are the lengths of the parasympathetic division of the ANS?

long preganglionic and short postganglionic fibers

What are the lengths of the sympathetic division of the ANS?

short preganglionic fibers and long postganglionic fibers

Where are the ganglia of the parasympathetic division of the ANS located?

the visceral effector organs

Where are the ganglia of the sympathetic division of the ANS located?

lay close to the spinal cord

What is dual innervation? Which organs receive it?

innervation by both sympathetic and parasympathetic, producing a dynamic antagonism allowing visceral activity to be precisely controlled, most body organs

What is sympathetic innervation? Which organs receive it?

controlled by regulation of the "tone" of the sympathetic system; sweat glands, adrenal medulla, arrector pili mm, many blood vessels

Which system in the ANS is dominated by E situations? What are they?

dominance by the sympathetic system is caused by physical or emotional stress

ex. emergency, embarrassment, excitement, exercise

What happens during an alarm reaction/flight or fight response?

Dilation of pupils, increase of heart rate, force of contraction & BP, decrease in blood flow to nonessential organs, increase in blood flow to skeletal and cardiac muscle, airways dilate and respiratory rate increases, blood glucose level increases

What is the purpose/ main function of the cerebrum/cerebral cortex?

Voluntary movements

Communcation

Memory

Understanding

Self-awareness

List area within the cerebal cortex and their functions

refer to study guide and mirror

What areas are asscociated with speech and what is their functions

Broccas area - Controls muscle for speech

Wernicke area - Vocab bank

Cerebral hemispheres

The left and right halves of the brain that control opposite sides of the body.

Cerebral cortex

The brain's outer layer (gray matter) that processes motor and sensory information.

Motor areas in the cortex

Control voluntary muscle movements.

Sensory areas in the cortex

Receive and process sensory input like touch, temperature, and pain.

Limbic system

The part of the brain that controls emotions and memory.

Brain stem

Basic life functions like breathing, heartbeat, and blood pressure.

Diencephalon

Part of the brain above the brain stem; includes thalamus, hypothalamus, and epithalamus.

Thalamus

Relays sensory and motor signals to the cerebral cortex.

Hypothalamus

Regulates homeostasis, hunger, thirst, temperature, and hormones.

Epithalamus

Controls the pineal gland, which makes melatonin and regulates sleep.

Parts of the brain stem

Midbrain, pons, and medulla oblongata.

Midbrain

Controls eye movement and processes visual/auditory info.

Pons

Helps with breathing and relays messages between brain and spinal cord.

Medulla oblongata

Controls heart rate, breathing, and blood pressure (homeostasis).

Cerebellum

Coordinates fine and gross motor skills and maintains balance.

Brain protection

Skull, meninges, blood-brain barrier, and cerebrospinal fluid (CSF).

Gyri, Sulci, and Fissures

Gyri = ridges; Sulci = grooves; Fissures = deep grooves in the brain.

Somatic nervous system

Controls voluntary movements and uses one heavily myelinated neuron.

Autonomic nervous system

Controls involuntary actions like smooth/cardiac muscle; uses two neurons with light myelination.

Sensory adaptation

When your body gets used to a stimulus (e.g., bright sun in your eyes).

Afferent vs. Efferent

Afferent = sensory input to brain; Efferent = motor output from brain.

First five cranial nerves

I - Olfactory, II - Optic, III - Oculomotor, IV - Trochlear, V - Trigeminal.

Cranial nerve #10

Vagus nerve - controls heart, lungs, and digestion.

Number of cranial and spinal nerves

12 cranial nerves and 31 spinal nerves.

Spinal nerve classification

Named by the vertebrae above where they exit the spinal cord.

Stronger autonomic branch

Parasympathetic (rest and digest).

Pain threshold vs. Pain tolerance

Threshold = point where pain is felt; Tolerance = how much pain you can handle.

Main neurotransmitters

Acetylcholine, norepinephrine, dopamine.

Dorsal vs. Ventral roots

Dorsal = sensory input; Ventral = motor output.

Sensory receptors

Detect stimuli like temperature, pressure, or pain in the peripheral system.

Reflex arc parts

Receptor, sensory neuron, integration center, motor neuron, effector.

Muscle spindle

A receptor that senses stretch in muscles.