Chapter 13 - The Central Nervous System Flashcards
CNS
brain + spinal cord
Rostral, Caudal, Cephalic
Brain is involved with the most complex functions: intelligence, consciousness, memory, sensory-motor integration, etc.
Adult brain weights about 1500 g (3.3 lbs)
encephalos = brain
Rostral
toward the snout (nose)
describes higher brain regions
Caudal
toward the tail
Cephalic
Of or relating to the head
Located on, in, or near the head
Embryonic Development of the Brain
neural tube primary brain vesicles (week 4): forebrain, midbrain, hindbrain seconday brain vesicles (week 5) adult brain structures adult neural canal regions
Organization of the brain
Brain is classified according to 4 parts
cortex
brain nuclei
Brain is classified according to 4 parts
Cerebral hemispheres
Diencephalon
Brain Stem
Cerebellum
Cerebral hemispheres make-up
cerebrum
Diencephalon make-up
thalamus + hypothalamus + epithalamus
Brain stem make-up
midbrain + pons + medulla
cortex
external sheet of gray matter at surface of brain
brain nuclei
groups of neuron cells bodies
interior gray matter of the brain
Brain ventricles
Expansions of brain's central cavity Filled with cerebrospinal fluid (CSF) continuous with each other and with central canal of spinal cord Lateral ventricles Third ventricle Fourth ventricle
Lateral ventricles
Located in cerebral hemispheres
3rd ventricle
located in diencephalon
4th ventricle
located in the hindbrain (dorsal to the pons and superior half of the medulla)
Cerebrum
Largest and most obvious portion of brain
accounts for about 83% of the brain’s weight
consists of left and right hemispheres, separated by longitudinal fissure
BUT not completely separated due to corpus callosum (large tract of white matter), which connects 2 sides
Higher brain functions (specific to lobes)
Cerebrum lobes
frontal parietal temporal occipital insula
Frontal lobe
forms the anterior portion of each cerebral hemisphere
Is separated from parietal lobe by central sulcus which runs along coronal plane
Initiates voluntary motor impulses for control of skeletal muscle
Analyzes some sensory info
personality
Speech is controlled here by Broca’s area
Parietal lobs
dorsal to central sulcus, frontal lobs
cutaneous and muscle sensations
understanding and listening to speech
Temporal lobe
separated from fontal lobe by lateral sulcus (fissure)
responsible for hearing - raw data only, recieves sounds
memory of audio/visual perceptions
Wernicke’s area - directly connected to the motor speech area
aphasia
aphasia
speech/language disorders caused by damage to specific areas of the brain
Occipital lobe
most dorsal lobe
responsible for vision
Insula lobe
deep lobe that cannot be seen on surface function not as clear, appears to be involved in integration of other cerebral activities and memory
Cerebrum layers
Cerebral cortex
white matter
deep gray matter
Cerebral cortex (conscious mind)
outer layer - gray matter (nerve cell bodies)
has many folds and grooves called convolutions which serve to triple the area
elevated folds (ridges) of the convolutions are called gyri
depressed grooves are called sulci
lateralization of function
3 functional areas
gyri
elevated folds of the convolutions
sulci
depressed grooves
Lateralization of function (cerebrum)
hemispheres control opposite sides of body
2 hemispheres are similar in structure and share most functions due to commissures
left hemisphere of cerebral cortex
language, math, logic
right hemisphere of cerebral cortex
visual-spatial, intuition, art, music
3 kinds of functional areas in the cerebral cortex
sensory areas
association areas
motor areas
sensory areas
allow awareness of sensation
each of the major senses has a sensory area
Associations areas
Integrate information
each of the major senses has an association area linked to ites primary sensory cortex
Motor areas
frontal lobe
control voluntary motor functions
Primary somatosensory cortex
parietal lobe
postcentral gyrus; skin and proprioceptive info
somatotopy: body mapping (homunculus)
Somatosensory association cortex
parietal lobe
posterior to primary somatosensory cortex
integration of sensory input
Visual areas
vision
occipital lobe
Auditory areas
hearing
temporal lobe
gustatory cortex
taste
roof of lateral sulcus
vestibular cortex
balance
insular lobe
olfactory cortex
smell
piriform lobe
rhinencephalon
rinencephalon
nose brain
connects to limbic system
smells can trigger emotions
Primary motor cortex
primary motor area located along precentral gyrus of frontal lobe
large neurons called pyramidal cells signal motor movements (voluntary)
motor homunculus
map of body
Premotor cortex
anterior to precentral gyrus
deals with more complex movements, planning
Frontal eye field
motor area
Broca’s area
motor area
cerebral white matter
inner layer
consists of myelinated axons
deep gray matter (3)
basal ganglia
basal forebrain nuclei
claustrum
basal (forebrain) nuclei
4 separate structures
anterior and doral to hypothalamus
arousal, learning, memory, motor control
Basal ganglia
3 separate structures
located in white matter
communicate with cerebral cortex; exact roles unknown-help to control movements
NOT the same as ganglia in PNS
Diencephalon
Forms central portion of forebrain
Surrounded by cerebral hemispheres
3 paired structures: thalamus, hypothalamus, epithalamus
thalamus
80% of diencephalon
egg-shaped
afferent impulses from senses
Hypothalamus
inferior portion of diencephalon
pituitary gland projects inferiorly (hormones)
contains many nuclei and is responsible for control of autonomic nervous system, emotional responses, body temp, hunger/thirst, behavior, sleep-wake cycles, endocrine system, and memory
Epithalamus
most dorsal
one group of nuclei and the pineal gland
secretes melatonin
Brain stem
Produces automatic behaviors necessary for survival
acts as passageway for all tracts running from cerebrum to spinal cord
involved with innervation to face and head
same structural plan as spinal cord - outer white matter surrounds inner gray matter
midbrain
involved with locomotor function and auditory postural, and visual functions
Pons
bridge connecting 2 sides of cerebellum
is a relay center for cranial nerves to areas in head
assists medulla in respiratory control (rate and depth of breathing)
Medulla oblongata
most caudal part of brain stem
continuous with spinal cord at foramen magum
contains never tracts that run between brain and spinal cord
made up of both white matter and gray matter, which is where nuclei for cranial nerves are located
major center for autonomic function (cardiac, resp, vasomotor)
Decussation
allowing one side of the brain to receive info from and send info to the other side of the body
Cerebellum
11% of the brain’s mass
Dorsal to pons and medulla
smoothes and coordinates body movements
3 regions: outer cortex (gray), internal white matter, and deep nuclei (gray)
commands come FROM frontal lobe of cerebrum and go TO cerebellum
Processes impulses from proprioceptors (within tendons, joints, etc. areas sensitive to tension)
Dysfunction
jerky, uncoordinated movements known as ATAXIA (similar to being intoxicated)
Functional brain systems
limbic system
reticular formation
Limbic system
group of structures in medial sides of cerebral hemispheres and diencephalon
components form ring in cerebrum
Is emotional brain, also involved with memory
communicates with many other brain regions; output mostly goes through hypothalamus and reticular formation
amygdala
part of limbic system
processes fear and response to fear
Reticular formation
through central core of medulla, pons, and midbrain
cluster of neurons with long axons that connect all over brain
reticular activating system (RAS) communicates with cerebellum and controls consciousness (severe injury can cause coma)
Brain Protection
meninges
cerebrospinal fluid
blood brain barrier
meninges
3 connective tissue membranes that lie external to brain and spinal cord
Dura mater
Pia mater
Arachnoid mater
Dura mater
periosteal layer is in contact with bone
meningeal layer forms external covering of brain
the 2 layers are fused except where sinuses formed
composed of dense CT
cranial dura mater has 2 layers, but spinal has one
Arachnoid mater
located deep to dura mater - spaces in between dura mater and arachnoid are subdural spaces, containing fluid film
Is net-like and contains subarachnoid space which contains CSF
Subarachnoid space has weblike strands that connect arachnoid and pia mater
Pia mater
latin pia: soft, tender, gentle
located directly on top of brain, spinal cord (bound to both) - clings tightly
made of modified loose CT
Cerebrospinal fluid (CSF)
a filtrate of blood, but it’s clear
mostly made of water and small molecules
total CSF at any one time ~150ml (1/2 cup)
CSF functions
protection and maintenance of brain and spinal cord provides cushioning (brain weighs 1.5 kg but in fluid it weighs .05 kg) provides nourishment and waste removal
CSF location
brain = outside in subarachnoid space and inside in ventricles
spinal cord = outside in subarachnoid space and inside in central spinal canal
Circulation of CSF
made in choroid plexus
travels through ventricles and into central spinal canal
goes to subarachnoid space of spinal cord then of brain
gets dumped into CV system via subarachnoid villi, which dump into veins
Blood Brain Barrier (BBB)
Arrangement of capillaries, CT, and astrocytes
Is a filtering system that keeps out certain cells and proteins, toxins, some drugs
Allows in gases, glucose, ions, lipids, alcohol (fat-soluble substances allowed in because they can diffuse across cell membranes)
Is absent in certain brain areas because brain must be able to react to circumstances (hypothalamus)
Spinal Cord
Runs through vertebral canal from foramen magnum to the level of L1/L2
protected by bone, meninges, and CSF
Dura mater=spinal dural sheath (diff than dura of brain)
Spinal cord functions
sensory and motor innervation of body (inferior to head)
provides 2-way path for body-brain signals
center for reflexes
Spinal cord structural make-up
31 pairs of spinal nerves attach to spinal cord through dorsal and ventral nerve roots
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
cauda equina
horse’s tail
collection of nerve roots at caudal end of spinal cord
Spinal cord gray matter
Inner region mostly neuron cell bodies
Forms ‘H’ - crossbar is called gray commissure; contains central conal, 2 posterior horns, 2 anterior horns
Lateral horns exist in thoracic and superior lumbar segments
posterior horns = mostly interneurons receiving info from sensory neurons
anterior and lateral horns = cell bodies of motor neurons, send axons out via ventral roots
Spinal cord white matter
myelinated and unmyelinated axons that allow communication between spinal cord and brain and between different spinal cord segments
Sensory and Motor pathways
most decussate (cross from one side to the other) from one side of CNS to other side
Most are made up of a chain of 2-3 neurons that contribute to successive tracts
Most exhibit body mapping
All pathways are paired right and left
Dyskinesia
degenerative condition of basal ganglia
Parkinson’s disease
slow, jerky movements
muscle rigidity
difficulty initiating voluntary movement
Huntington’s disease
Overstimulation of motor activities
Limbs jerk uncontrollably
Inherited - genetic defect is known
Meningitis
Inflammation of meninges caused by bacterial or viral infections
Can spread and cause inflammation of brain (encephalitis)
Hydrocephalus
Excessive CSF in ventricles or subarachnoid space
Puts pressure on the brain
Traumatic brain injuries (3)
concussion
contusion
hemorrhaging
concussion
symptoms mild and transient
contusion
destruction of brain tissue
Hemorrhaging
bleeding from ruptured vessels into subdural or arachnoid
swelling can occur
Degenerative brain diseases
cerebrovascular accident (CVA) Alzheimer's disease
Cerebrovascular accident (CVA)
blockage/interruption of blood flow to brain (clot or burst vessel)
Ischemia
lack of blood to tissue, then no oxygen
Alzheimer’s disease
Progressive generative disease loss of memory short attention span depression disorientation - basal nuclei involved
Spinal cord damages
paralysis
paresthesia
paraplegia
quadriplegia
motor neurons to diaphragm are in C3-C5; breathing affected
paralysis
loss of motor function
paresthesia
abnormal/lost sensation
Paraplegia
damage between T1-L2
lower limbs affected (not upper)
quadriplegia
damage to cervical region
All 4 limbs affected
