Nervous System Part 2

What are sensory fibers?

afferent and bring info to CNS

What are motor fibers?

efferent and take info away from CNS

What are mixed nerves?

sensory and motor fibers

What is a nerve?

collection of nerve fibers (axons) covered in connective tissue

What is epineurium?

covers nerve

What is perineurium?

covers fascicle

What is endoneurium?

covers neuron

What is the pathway of a nerve?

receptor, sensory neuron, interneuron, motor neuron, effector

Where is the interneuron?

within spinal cord and brain

What are reflexes?

autonomic, subconscious responses to stimuli within or outside the body

What is the knee jerk reflex?

1 sensory neuron and 1 motor neuron, helps maintain posture by bending of the knee which causes the reflex to stimulate quadriceps femoris upright

What is the withdrawal reflex?

step on sharp object, 1 sensory neuron and 1 interneuron and 1 motor neuron, limits tissue damage

What are meninges?

layered membranes that lie between bony covering and soft tissues of CNS

What are the 3 layers of meninges?

dura mater, arachnoid mater, pia mater

What is the dura mater?

outermost layer, has 2 layers, tough fibrous connective tissue, lots of blood vessels and nerves, between some lobes of brain to separate them, has epidural space to separate the spinal cord

What are the 2 layers of the dura mater?

periosteal and meningeal

What is periosteal?

attached to inside of skull, not in spinal cord

What is meningeal?

covers brain and spinal cord

What is the arachnoid mater?

thin, weblike, no blood vessels, does not enter the small grooves in brain, separated from pia mater by subarachnoid space which is filled with cerebrospinal fluid

What is the pia mater?

very thin layer that clings tightly to brain and spinal cord, many blood vessels and nerves

What is subdural hematoma?

bleeding from brain blood vessels which causes pressure that could cause death of brain tissue

What is an epidural?

anesthesia given in the epidural space during childbirth and spinal/hip/leg surgeries

What are advantages of an epidural?

decreased risk compared to general anesthesia, better pain management and less blood loss

What is the spinal cord?

begins where nervous tissue leaves skull at level of foramen magnum, ends in tapered point at L2, has conus medullaris and cauda equina

What is the conus medullaris?

tapering end section

What is the cauda equina?

horse’s tail, collection of nerves at end of vertebral canal

What is the structure of the spinal cord?

has 31 segments each with a pair of spinal nerves, has a cervical and lumbar enlargement

What is the cervical enlargement?

thickening that supplies nerves to upper limbs

What is the lumber enlargement?

thickening that supplies nerves to lower limbs

What is the cross section?

butterfly shaped core of gray matter within white

What is the gray matter part in the cross section?

contains posterior and anterior horns which are mostly interneurons

What is the white matter in the cross section?

contains anterior, posterior, and lateral funiculi

What is the funiculus?

tracts which are long bundles of myelinated nerve fibers, central canal which is filled with cerebrospinal fluid

What are the 2 major functions of the spinal cord?

conduct impulses and center for spinal reflexes

What are the 2 nerve tracts?

ascending and descending

What are ascending nerve tracts?

carry sensory info to brain

What are descending nerve tracts?

carry motor info to effectors

What are the 4 major sections in the brain?

cerebrum, diencephalon, brainstem, and cerebellum

What is the cerebrum?

sensory and motor nerve functions and higher thinking, memory and reasoning

What is the diencephalon?

processes sensory information

What is the brainstem?

pons + midbrain + medulla oblongata, connects other parts of nervous system, regulates visceral organ activities

What is the cerebellum?

coordinates voluntary muscular movement, mostly white matter with thin gray cerebellar cortex on surface, reflex center for integrating sensory info (position of body parts), coordinates activities needed for complex smooth movement, helps maintain posture and balance

What is the structure of the cerebrum?

2 cerebral hemispheres connected by corpus callosum, separated by layer of dura mater

What are the landmarks on the cerebrum?

gyrus (ridge), sulcus (shallow groove), and fissure (deep groove)

What are the 5 brain lobes?

frontal, parietal, temporal, occipital, insula

Where is the insula located?

buried deep in lateral sulcus

What is the cerebral cortex?

outermost part of cerebrum, has 75% of neurons in the body, follows all dips and convolutions in brain’s surface

What is the under cortex?

white matter which makes up most of the cerebrum and myelinated axons

What are the 7 functions of the cerebrum?

provides higher brain functions, centers for interpreting sensory input, centers for coordinating motor output, memory, reason, intelligence, personality

What are the 3 main functional areas of the cortex?

motor, sensory, and association

What is the motor area?

in the brainstem tracks from right hemisphere cross over to control left side of body and vice versa

What is the primary motor area?

lies in frontal lobe, skeletal function

What is the Broca’s area?

speech

What is the frontal eye field?

voluntary movement of eye

What is the premotor area?

repetitive movements like typing

What is the sensory area?

conscious awareness of sensation, lie in several lobes, cross over in spinal cord or brainstem

What is the primary somatosensory?

skin sensations

What is the visual area?

sensory input from eyes compared to visual “memory”

What is the auditory area?

hearing

What is the olfactory area?

smell

What is the gustatory area?

taste

What is the motor and sensory funiculus?

mapped on cortex by representative percent of body

What are the association areas?

neither primarily sensory nor motor, analyze and interpret sensory experiences, oversees: memory, reasoning, verbalizing, judgement, and emotion

What is the prefrontal area?

higher intellect, cognition, personality

What is the Wernicke’s area?

sounding out unfamiliar words

What is the Broca’s area?

speech production

What is the general interpretation area?

integrates info from many sensory areas at once

What is the visceral association area?

conscious interpretation of visceral sensations like upset stomach, full bladder, etc.

What is in the left side of the brain?

language, math, and logic

What is in the right side of the brain?

art, music, intuition, emotion

What are ventricles?

spaces within the brain that are continuous with central canal of spinal cord, filled with cerebrospinal fluid and lined with ependymal cells

What is the path of cerebrospinal fluid?

large lateral ventricles, interventricular foramen, third ventricle, cerebral aqueduct, fourth ventricle (subarachnoid space of brain which is reabsorbed into blood), and spinal cord

What is hydrocephalus?

“water on the brain”, accumulation of cerebrospinal fluid in the ventricles, creates pressure on brain tissue, treated with a shunt

What is a shunt?

a tube that drains cerebrospinal fluid into abdominal cavity

What is diencephalon?

located between hemispheres and above midbrain, contains thalamus and hypothalamus

What is the thalamus?

receives all sensory input, except smell

What is the hypothalamus?

maintains homeostasis by linking nervous and endocrine systems, regulates autonomic functions

What are the 9 functions of the hypothalamus?

heart rate, digestion, blood pressure, body temperature, water and electrolyte balance, hunger, sleep and wakefulness, emotional responses, biological drives

What is the epithalamus?

has pineal body and choroid plexus

What is a pineal body?

secretes melatonin for sleep

What is a choroid plexus?

secretes cerebrospinal fluid

What are the 3 parts of the brainstem?

midbrain, pons, and medulla oblongata

What is the midbrain?

reflex centers for eye and head movements

What is the pons?

transmits impulses between cerebrum and other part of the nervous system, contains centers that help regulate rate and depth of breathing

What is the medulla oblongata?

transmits all ascending and descending impulses, reflex centers for force and rate of heart contraction, rate and depth of breathing, vomiting, sneezing, etc

What is the peripheral nervous system?

nerves that branch out from CNS to the body, cranial nerves (12 pair) + spinal nerves (31 pair)

What are the 2 subdivisions of the peripheral nervous sytem?

somatic and autonomic

What is the somatic system?

conscious, skin and skeletal muscles

What is the autonomic system?

unconscious, automatic, visceral organs

What are cranial nerves?

arise from underside of brain, most are mixed nerves, some motor and others sensory, sensory fibers in cranial nerves have cell bodies outside brain in ganglia, motor fiber nerve cell bodies in gray matter

What does cranial nerve #1 do?

originates in cerebrum

What does cranial nerves 2-12 do?

originate in brainstem

What are spinal nerves?

31 pairs mixed nerves, grouped according to the level they arise from (cervical, lumbar, sacral, coccygeal)

What is the dorsal root?

with dorsal root ganglion, cell bodies of sensory neurons going to CNS

What is the ventral root?

axons of motor neurons with cell bodies in spinal cord gray matter

How do you make a spinal nerve?

dorsal root plus ventral root

What are plexuses?

network of spinal nerves not found in thoracic region

What is the cervical plexus?

deep in neck, serve the muscles and skin of neck, also some fibers join phrenic nerves to supply diaphragm

What is the brachial plexus?

deep in shoulder between neck and armpit, serve muscles and skin of arm, forearm, and hand

What is the lumbosacral plexus?

supply muscles and skin of lower abdominal wall, genitalia, buttocks, thighs, legs, feet