The Central Nervous System

What are the 4 main parts of the brain?

• cerebrum

• diencephalon

• brain stem

• cerebellum

What are meninges?

connective tissues covering the brain to protect it

What are the meninges from most superficial to deepest? Describe them

• dura mater - durable, tough

• arachnoid matter - thin

• pia mater - thin

• layers of connective tissue

What are ventricles?

CSF filled spaces within the brain

What are the main ventricles of the brain?

• lateral ventricles - within cerebral hemispheres

• 3rd ventricles - in diencephalon behind thalamus

• 4th ventricles - between brain stem and cerebellum

What are the functions of the circulation of Cerebrospinal Fluid (CSF)?

• protect/cushion the brain by allowing it to float

• provides nutrients to ependymal cells

• eliminates waste products

What is the choroid plexus?

• blood vessels and the ependymal cells lining them

• create CSF from things in blood

Describe ependymal cells in the brain

• line blood vessels like epithelial cells

• prevent cells from going into CSF, allow only liquid and gases

• held together by tight junctions to stop paracellular movement

Describe the movement of CSF in the brain

• created in the choroid plexus (blood vessels and ependymal cells) at the lateral ventricles

• flows to third ventricle

• to cerebral aqueduct

• to fourth ventricle

• to sub arachnoid space

• back into blood through dura mater

What is the blood brain barrier and what creates it?

• provides constant and protected extracellular enviornment in the CNS

• created by tight junctions between epithelial cells of blood vessels

• thick basement membrane of capillary wall

• astrocytes signal epithelial cellss, affecting the permeability of tight junctions

How do substances pass through the blood brain barrier?

• lipid-soluble substances, ie, gases, alcohol, cross through

• lipid-insoluble substances transported through, ie. glucose

What are the regions of the cerebrum and what do they control?

• frontal lobe - cognition, personality, memory, thinking, voluntary motor control

• insula

• parietal lobe - sense of touch, spatial awareness, somatosensory

• temporal lobe - processing hearing, language, forming memories

• occipital lobe - visual cortex

What is gray matter in the brain?

• cortex (collections of cell bodies along lining of brain)

• basal nuclei (deep gray matter)

What is white matter in the brain?

• tracts

• commissures

Describe the primary motor cortex

• superficial part of the frontal lobe

• right side controls left side of body and vice versa

• more neurons/space on cortex devoted to areas with more fine motor control

• corticospinal tracts project into the spinal cord

What are corticospinal tracts?

nerves (axons) that carry voluntary motor commands from the motor cortex in the frontal lobe into the spinal cord

Describe the primary somatosensory cortex

• superficial part of parietal lobe

• each hemisphere receives sensory info about touch, temp, pain, itch, body position, from skin/joint/muscles from opposite side of the body

• communicates with other parts of the brain through association neurons

• more neurons/cortex space to process snesory info for more sensitive body parts

What are association areas in the brain?

• areas that integrate inputs

• give meaning to info received, store in memory, tie to experiences, decide on actions

• where emotions and thoughts become conscious ex. putting words to things, thinking about what you want to do

• often in the same lobe as associated cortex

What cortical areas are associated with language and where are they located?

• broca’s area - motor output of being able to speak, in frontal lovelobe

• wernicke’s area - understand language, in temporal lobe

Describe Receptive (Wernicke’s) aphasia and expressive (broca’s) aphasia

• receptive - damage to wernicke’s area, meaningless speech, cant undersant

• expressive - damage to broca’s area, understand but cant respond

What is basal nuclei?

• deep grat matter

• involved with motivation, motor planning, and attention

• connect back to motor cortex to actually move

How is Parkinson’s disease caused by problems in the basal nuclei?

• degeneration of dopamine-releasing neurons in the midbrain to the basal nuclei (essential for motor output)

• basal nuclei deprived of dopamine become overactive, causing tremors and difficulty with intentional movements

What is white matter in the CNS, including the types of tracts?

• axons

• myelinated fibers bundled into tracts

• association tracts - send signals between parts of cortex

• commisural tracts - connect 1 side of the brain to the other (ex. corpus callosum)

• projection tracts - connect cortex to other parts of the CNS (travel superior to inferior and vice versa)

What are the parts of the brain stem?

• midbrain

• pons

• medulla oblongota

What are the parts of the diencephalon?

• thalamus

• hypothalamus

• pineal gland

What does the thalamus do?

• relay center in center of brain

• almost all sensory info and some motor info goes to the thalamus before going to the cortex

• process sensory, auditory, and visual inputs

• full of groups of nuclei regulating different functions

what does the hypothalamus do?

• basal homeostasis and autonomic functions

• different nuclei regions for regulating different

• regulates feeding, fight/flight response, sex, energy balance (Feeding and metabolism)

• water balance

• body temp

• sleep/wake cycles

• reproduction

What is the limbic system?

• multiple structures in brain connected through the fornix to the hypothalamus

• process emotional experiences

• important for learning and memory

• can send signals to hypothalamus that can cause autonomic/physiological responses to emotional signals

What does the pineal gland do? Describe the hormone

• makes melatonin

• melatonin regulated by light, increases when its dark outside

• light inhibits pineal gland hormone production

Describe the brainstem

• brainstem nuclei involved with sensory or autonomic functions

• project tracts run through to connect brain and spinal cord

• Pons bridges brain stem and cerellum through fibers/axons/tracts

• also has grey matter (nuclei)

• regulates and maintains basic body functions like breathing

Describe the cerebellum

• lots of surface area, lots of sulci and gyri

• responsible for coordination of voluntary motor control, motor memory, final motor control, balance

What is an EEG?

• measures collective graded potentials of nuclei in cortex (excitatory or inhibitory)

Describe the brain waves classes shown in EEGs and what they mean

• alpha waves - awake but realzed, high frequency, low amplitude due to constant ISPS and ESPS

• beta waves - awake but alert, veyr high frequency but lower amplitude due to constant ISPS and ESPS

• theta waves - equalish signals, common in children

• delta waves - deep sleep, very high amplitude due to all hyperpolarizing or all depolarizing potentials at the same tinem

Describe the main stages of sleep

• REM sleep - all movement except eyes inhibited, high HR, brain activity has very high frequency like when awake

• NREM sleep - movement occurs, HR is slower, most vivid dreaming

What is reticular formation?

• brainstem nuclei involved with attention and autonomic functions

• signals cortex in non-specific way to keep brain active ex. sitting in an area with lots stuff going on is overstimulation

• sleep turns off signals from basal nuclei to cortex

Describe adenosine in the brain and its antagonist

• adenosine - ATP byproduct that makes you sleepy, the more energy you use the more you make

• caffeine - adenosine antagonist, blocks adensoine receptors to keep you alert