PHYL 141 Chapter 14 & 15

(CNS) central nervous system:

brain and the spinal cord

(PNS) peripheral nervous system:

spinal nerves & cranial nerves

Brain has four main regions:

1. cerebrum

2. Diencephalon

3. cerebellum 

4. brain stem

Diencephalon

3 parts

Thalamus

Hypothalamus

Epithalamus (pineal gland)

Thalamus

• paired masses of gray matter on sides of third ventricle

• sorts and relays sensory information (except olfactory)

• Relay center

Hypothalamus

• Located: anterior-inferior to thalamus

• regulates homeostatic functions; controls ANS, regulates emotional states, controls sleep/wake cycles, controls endocrine system; regulates body temperature/hunger/satisfaction/water balance/thirst

Epithalamus

• covers third ventricle; roof of diencephalon

• pineal gland: secretes melatonin (regulating day/night cycles)

The brain is protected by:

1. Cranium

2. Meninges

3. Cerebrospinal fluid

4. Blood-brain barrier (BBB)

Cranium

skull bones that gives solid support

Meninges:

connective tissue that forms a series of membranes (layers) surrounding the brain. Pia, arachnoid, dura mater.

Cerebrospinal fluid (CSF):

helps protect brain and spinal cord by -shock absorbing

Blood-brain barrier (BBB): 

prevents the entrance of dangerous materials from the blood into the brain.

Cranial Meninges: Three layers (deep to superficial):

1. Pia mater

2. Arachnoid mater

3. Dura mater

Pia mater:

deepest, innermost layer

• follows contours of the brain 

• provides passageway for blood vessel penetration

Arachnoid mater:

middle layer

• Subarachnoid space: between arachnoid and pia mater 

• Contains cerebrospinal fluid (CSF)

• CSF is the liquid cushion to brain and spinal cord

• Arachnoid villi: CSF filtered back into blood through villi

Dura mater:

outermost layer, toughest.

• Meningeal layer (deeper) & Periosteal layer (internal surfaces of cranial bones)

• Epidural space: between dura mater and skull; contains large arteries that nourish meninges

• Sinuses: created by dura folds

Dura mater extensions: 

Falx cerebri: separate 2 cerebral hemispheres

Falx cerebelli: separates 2 cerebellar hemispheres 

Tentorium cerebelli: separates cerebellum & cerebrum

Ventricles

• Cavities within brain that connect with each other & the spinal cord

• Lined with ependymal cells (specialized neuroglia)

• Filled with CSF

1 & 2: Lateral ventricles: 

Found in each cerebral hemisphere, separated by septum pellucidum (membrane separating b/t the two lateral ventricles)

 Third ventricle: 

From the lateral ventricles (through the interventricular foramen), the third ventricle arises.  

Fourth ventricle 

From the third ventricle, CSF flows through the cerebral aqueduct to the fourth ventricle (found between pons and cerebellum) & then merges with central canal of spinal cord

Cerebrospinal Fluid (CSF) Circulation

1. Functions:

• Reduce weight of the brain

• Provide cushion

• Transport oxygen and nutrients to and waste from brain

CSF is formed when

blood plasma is filtered through capillaries and modified by specialized ependymal cells in the choroid plexus in each ventricle

CSF is circulated through

the ventricles, into the subarachnoid space (where waste is removed), through the arachnoid villi, draining into the dural venous sinuses and then filtered back into the blood

• Lateral ventricles → interventricular foramen → third ventricle → cerebral aqueduct → fourth ventricle → central canal (of the spinal cord)

Hydrocephalus:

blockage of CSF circulation causing excess of CSF in brain or lack of flow leading to elevated pressure in the brain which causes damage or death

CSF is continuously being

formed, circulated, and reabsorbed:

CSF circulation passes from the (flow of CSF)

lateral ventricles (through the interventricular foramen) to the third ventricle (and through the cerebral aqueduct) into the fourth ventricle. 

CSF moves into the

subarachnoid space

Waste removal: (CSF)

as CSF flows through the subarachnoid space, waste products are removed

CSF Passes through the ——- draining into the ?

arachnoid villi, dural venous sinuses

? filter CSF back into the blood

dural sinuses

CSF continues to the spinal cord (through the ?)

central canal

Choroid plexus: 

• Produces CSF in each ventricle. 

• CSF is then reabsorbed into the blood at the arachnoid granulations villi

BBB stands for?

blood brain barrier

What is the BBB?

Physical barrier to protect neurons from waste products, hormones, or drugs that are circulating in the blood

bbb is formed by

astrocytes (glial cells)

• Extensions of astrocytes secrete chemicals that influence capillary endothelial cells to form tight junctions, which

(BBB)

• limit what substances can pass out of the blood

What compounds can cross the BBB?

Lipid-soluble compounds (gases, alcohol, nicotine)

Gray matter: 

• cell bodies of neurons, dendrites, and unmyelinated axons

White matter: 

• myelinated nerve axons

• Connects various components of the nervous system

Cerebral cortex

: extensive folded surface (on cerebrum); increases surface area.

Where is the precentral gyrus located?

frontal lobe

postcentral gyrus location?

Parietal lobe

frontal lobe functions

• motor control (e.g. speech, reasoning, personality, etc.)

• Precentral gyrus: voluntary motor movement on the body's contralateral side

parietal lobe functions

• sensory information (e.g. touch, temperature, pain, itch) 

• language understanding. Sensory homunculus: processing power devoted to areas of the body mapped

• Postcentral gyrus: primary somatosensory cortex (significant brain region responsible for proprioception)

occipital lobe functions

• process visual information

Temporal lobe functions

process sound information, facial recognition, receptive area for smell

Insula

• process taste, smell, sound, visceral/body surface sensations, and emotions

• Hidden under the parietal, frontal, and temporal lobes. 

primary somatosensory cortex;

sensory homunuculus,

• Broca’s Area:

• (44 & 45) in left hemisphere of frontal lobe; motor speech/controls muscles for vocalization

Wernicke’s Area:

( in left hemisphere near lateral sulcus and auditory cortex; comprehension of spoken and written language

Limbic System:

processes emotions (e.g. pleasure, anger, rage, hunger)

• Hippocampus: memory (new long-term memory)

• Amygdaloid body/amygdala: connects to hippocampus; regulates emotional states (fear)

Two cortical areas regulate speech

: Wernicke’s area and Broca’s area.

Wernicke’s 

Location: left hemisphere (near lateral sulcus and the auditory cortex)

• If damaged = difficulty processing information regarding the comprehension of spoken and written language; called receptive (Wernicke’s) aphasia. 

• Wernicke’s aphasia: “Word Salad”

Broca’s area

Location: left hemisphere of the frontal lobe

• The motor speech area; controls muscles needed for vocalization. 

• If damaged = experience problems when generating speech; called expressive (Broca’s) aphasia

• Broca’s aphasia: limited Speech, understand but can’t get words out.

Basal nuclei/ganglia:

masses of gray matter found within white matter of cerebrum

caudate: 

• just lateral to the lateral ventricle

• putamen:
  

• inferior to the caudate and separated by the large white-matter structure called the internal capsule

• globus pallidus:

• medial to the putamen

Frontal section of cerebral cortex and basal nuclei

Process motor and cognitive information; important for learning new motor skills

Motor processing regulated by dopamine

The cerebellum contains

half the brains neurons

motor functions of the cerebellum

 coordinating/optimizing movements; maintain posture/balance; fine motor adjustments

cerebellum non motor functions

learning and information processing; sleep-related functions

vermis (cerebellum)

runs along midline of cerebellar hemispheres

lobes of cerebellum

(anterior, posterior, flocculonodular) separated by fissures

cerebellum is connected to the brainstem via

the cerebellar peduncles, which facilitate communication between the cerebellum and other brain regions.

Cerebellar nuclei embedded into

arbor vitae (white matter in each hemisphere)

Cerebellum Folia

cerebellar cortex on surface of each hemisphere

Brain stem is located

between diencephalon and spinal cord

brain stem controls

• breathing, heart rate, blood vessel diameter

brainstem coordinates

• breathing, heart rate, blood vessel diameter

Several cranial nerves originate in the

brainstem

Brainstem parts (3)

midbrain, pons, medulla oblongata

Anatomy of the Pons

• cerebral peduncles

• superior colliculi

• inferior colliculi

• red nuclei and substantia nigra

• cranial nerves

cerebral peduncles:

connects upper and lower motor neurons

superior colliculi:

signals to move upper body, head, eyes in response to visual stimuli

inferior colliculi:

response to auditory stimuli; reflex of head in direction of loud noises

red nuclei and substantia nigra:

control motor activity

Cranial nerves:

• oculomotor and trochlear cranial nerves

Pons is the connection between

cerebral cortex, cerebellum, and other brain regions

cranial nerves in the pons

include the trigeminal, abducens, and facial nerves.

Effect of the pons

includes regulation of breathing, communication between cerebellum and cerebrum, and control of sleep.

medulla oblongata is continuous with the

spinal cord

medulla o. controls what?

coughing, sneezing, swallowing, vomiting, hiccuping reflexes; taste, hearing, and balance

anatomy of medulla oblongata

pyramids

corticospinal tracts

cranial nerves

pyramids

continuation of peduncles

corticospinal tracts produce signals that

control body movements

the cranial nerves associated with the medulla oblongata

vetibulocochlear, glossopharyngeal, vagus, accessory, hypoglossal cranial nerves

CN I

olfactory (smell)

CN II

optic (vision)

CN III

oculomotor (eye movement)

CN IV

trochlear (eye movement)

CN V

trigeminal (facial sensation and mastication)

CN VI

abducens (eye movement)

CN VII

facial (facial expression and taste)

CN VIII

vestibulocochlear (hearing and balance)

CN IX

glossopharyngeal (taste and swallowing)

CN X

vagus (autonomic functions and sensations)

CN XI

accessory (neck and shoulder movement)

CN XII

hypoglossal (tongue movement)