Chapter 12 (lectures)

1. Brain

2. Spinal cord

What makes up the central nervous system? [2]

Grey matter

Matter made of neuron cell bodies in the brain, brain stem, and spinal cord

White matter

Matter made of myelinated axons in the brain, brain stem, and spinal cord

Tracts or fiber tracts

Grouped axons in the CNS

Grey on outside, white on the inside

Arrangement of white and grey matter in brain

White on outside, grey on inside

Arrangement of grey and white matter in spinal cord

To produce cerebrospinal fluid in which brain sits in the skull

Key function of ventricles in the brain

1. Two lateral ventricles

2. Third ventricle

3. Fourth ventricle

Name ventricles in the brain [4]

Apertures connect the ventricles o the subarachnoid space that surrounds the brain

How does cerebrospinal fluid get into skull?

Cerebral cortex

Outer surface of the brain

longitudinal fissure

Separates right and left hemispheres of the brain

Gyri

Elevated structures on the surface of the brain

Sulci

Shallow grooves on the surface of the brain

To increase the brain’s surface area to allow for more cell bodies/grey matter, while still keeping the brain relatively small. Surface area is tripled.

Function of gyri and sulci on surface of the brain

1. temporal

2. frontal

3. parietal

4. occipital

5. + insula

Four main lobes of brain + tiny lobe when separated

Central sulcus

Sulcus that divides the frontal lobe from the parietal lobe

Lateral sulcus

Sulcus that divides the temporal lobe from the parietal and frontal lobes

1. lateral sulcus

2. central sulcus

Two major sulci covered in this course

1. Central cortex

2. Internal white matter

3. Basal ganglia

Three regions of brain hemispheres

Cerebral cortex

Part of brain where conscious mind is. Think, feel, remember, communicate, initiate movement. Accounts for 40% of brain mass

1. Motor

2. Sensory

3. Associatoin/integration

Three functional areas of the cerebral cortex

1. Primary motor cortex

2. Premotor cortex

3. Broca’s area

Motor areas of cerebral cortex [3]

Primary motor cortex

Motor area for conscious control of movement

Premotor cortex

Motor area where movement prep and planning takes place

Broca’s area

Motor area specifically for muscles that produce speech

Motor homunculus

Schematic that shows which parts of cortex control which parts of the body

1. Primary somatosensory

2. Auditory area

3. Wernicke’s area

4. Visual areas

Four sensory areas of the cortex

Primary somatosensory cortex

Impulses from general sensory receptors in the skin and from proprioceptors arrive here (sensory area)

Auditor area

Impulses from inner ear are projected here whrere they are “hear” and interpreted (sensory area)

Wernicke’s area

Sensory area responsible for understanding written and spoken language

Visual areas

Sensory area for sensation and interpreting what our eyes see

Olfactory area

Sensory area for impulses from receptors in the nasal cavity. End result is conscious awareness of different smells

Sensory homunculus

Schematic that maps parts of cortex that receive sensory information from different parts of the body

Vestibular (equilibrium) cortex

Cortex that keeps us upright. Sensory receptors are located in the inner ear. Balances against the pull of gravity.

Gustatory cortex

Cortex that allows conscious awareness of taste

Visceral sensory area

Sensory area that makes us consciously aware of visceral sensation (e.g., full bladder, upset stomach)

Multimodal association areas

Areas that receive inputs from multiple senses and send outputs to multiple areas. Gives meaning to information received.

Basal ganglia

A group of three nuclei deep in cerebral white matter that receive input from the cortex and provide output to motor cortex. Critical for voluntary movement, to initiate and execute. Plays role in learning and habit formation

1. Caudate

2. Putamen

3. Globus pallidus

Three nuclei that make up basal ganglia

Parkinson’s and Huntington’s

Diseases that are partly due to lesions in the basal ganglia area

Dienchephalon

Encloses the third ventricle

1. thalamus

2. hypothalamus

3. epithalamus

Three structures that make up the dienchephalon

Thalamus

“relay station” where all sensory information passes through. Funnels information to appropriate part of the cortex. Important for learning, memory, and new motor activity

hypothalamus

structure in front of the thalamus in dienchephalon

1. Visceral control centre

2. Initiates physical response to emotion

3. Controls autonomic nervous system

4. Regulates food intake (stops/starts hunger impulse)

5. Regulates water balance and thirst

6. Controls endocrine system function

7. Regulates body temperature

Functions of the hypothalamus[7]

Epithalamus

Tiny posterior structure in diencephalon, forms roof of the third ventricle.

Pineal gland

Gland close to the epithalamus that regulates sleep/wake cycle with hypothalamus by producing melatonin.

1. Midbrain

2. pons

3. medulla oblongata

Three structures that make up brain stem

Brainstem

Structure produces functions that are necessary for survival, pathways of tracts from the cortex to the spinal cord. Gives rise to 10 of 12 cranial nerves.

Pons (means bridge)

Structure in brainstem that is comprised of conduction fibers. Conducts between higher brain cells and spinal cord. Conducts between cerebellum and motor cortex

Medulla oblongata

Structure in brainstem that serves as many control centers that are necessary for life.

1. Cardiovascular center

2. heart rate and blood pressure

3. Respiratory center

4. Vomiting

5. Hiccups

6. Coughing

7. Sneezing (etc.)

Control centers in the medulla oblongata [at least 3]

Cerebellum (sometimes called little brain)

Tiny structure with many convulsions that is posterior to the brain stem. Shaped similarly to the brain, but smaller. Only 10% of the brain but 50% of its total neurons

1. Acts as a comparator that compares intended motion and makes corrections as needed

2. not part of conscious perception

3. Key role in timing and initiating movement

4. Cannot initiate movement

5. is easily disrupted by alcohol

Functions and characteristics of cerebellum (5)

1. limbic system

2. reticular formation

two functional brain systems mentioned in this course

Limbic system

Functional brain system located on the medial aspect of the cerebral hemispheres. Dubbed the “emotional visceral brain”

1. drives emotion and control of emotion

2. center for motivation and survival (eat and reproduce)

3. Ability to store memory

4. Ability to regulate behaviors (what is appropriate, what is not)

Functions of the limbic system [4]

Reticular formation

3 broad columns that run the lengths of the brains stems that have broad connections that allows system to govern arousal (alertness) of the brain as a whole. comes up through the brain stem and radiates out to cerebral cortex. Contains reticular activating system.

1. Continually sends signals to the cortex to keep it alert and conscious

2. Filters out unimportant sensory information (we would be bombarded by info if we didn’t)

3. Involved in control of movement

Functions of the reticular activating system (RAS) (3)

1. skull

2. meninges

3. cerebrospinal fluid

4. blood brain barrier

Four barriers that protect easily damaged nervous tissue

meninges

Layers of tissue that surround the brain, in three layers. Helps maintain shape and hold structure

Dura mater (“tough mother”)

Meninges layer that is immediately under bone. Periosteal layer and dural layer, collectively, are this:

Arachnoid mater (spider)

Feathery projections that connect to underlying pia layer, under dura

pia mater (“gentle mother”)

Very thin, not very strong meninges layer in comparison to others, but provides same protection

Subdural space

Space under dura mater.

Subdural hematoma

Bleeding into subdural space

Subarachnoid space

Space under arachnoid layer. Bleeds in blood vessels typically cause bleeding here

meningitis

Inflammation of meninges

Encephalitis

inflammation of brain itself

Cerebrospinal fluid

Fluid in which brain floats, surrounds brain and spinal cord

Choroid plexus

Produces cerebrospinal fluid, hangs from the roof of each of the ventricles

to cushion and nourish. Some ions and proteins are important for brain nourishment

Main function of cerebrospinal fluid

Every 8 hours

How often is cerebrospinal fluid replaced?

Blood brain barrier

Protects the brain from substances that are already in the body. Keeps unwanted molecules from entering the brain. Tight junctions instead of gap junctions. Very difficult for molecules to cross this barrier. Reason medications cannot easily get from the bloodstream to the brain

31 pairs

How many pairs of spinal nerves in spinal cord?

Cauda equina

Long nerve roots that travel down into the sacrum

During development, bony vetebral columb grows faster than the spinal cord. Spinal cord is relatively shorter.

Why doesn’t spinal cord go the length of the spine?

dorsal (posterior) horns

Cell bodies that carry sensory information from the periphery up to get to the brain. Carries sensory information only.

Ventral (anterior) horn

Cell bodies of motor neurons that bring information out to the periphery. Carries motor information only

Spinal nerve

Where dorsal and ventral roots combine sensory and motor information (still part of PNS)

Multi-neuronal pathways

Pathways with more than one neuron. Transmits information between the brain and periphery

1. Decussation: pathways cross from one side to the other at some ponit

2. Relay: most pathways consist of 2-3 neurons that convey info from one region to another

3. Somatotopy: fibers are arranged in an orderly fashion that reflects overall mapping of the body

4. Symmetry: all pathways and tracts are paired (right and left sides)

Four characteristics of multi-neuronal pathways

1. Ascending tracts

2. Descending tracts

Two kinds of tracts

Ascending tracts / pathways

Tracts carrying sensory information. Different senses travel in different pathways

Spinothalamic tract (Spinal cord to thalamus)

Ascending tract conveys temperature, pain, coarse touch, and pressure

Spinocerebellar tract (spinal cord to cerebellum)

Ascending tract conveys information about muscle tendon stretch (for coordinating movement)

Dorsal column

Ascending tract carries information about proprioception and discriminatory touch (distinguish what you are touching) and vibration

Descending tracts

Tracts that send information down, carrying motor information