Chapter 12 The CNS

Question 1

Brain Protection:

Answer 1

Brain is protected by bone, meninges, cerebrospinal fluid (CSF), and the blood-brain barrier

Question 2

Meninges

Answer 2

Meninges: Connective tissue membranes

* Dura mater 
* Arachnoid mater 
* Pia mater

Question 3

Meninges:

Dura mater

Answer 3

Dura mater = dense irregular connective tissue
thickest and most superficial
two layers fused together
**dural septa = partitions that extend into major brain fissures
**dural venous sinuses = spaces formed where two layers of dura mater are separated from each other
collect all venous blood exiting brain then drain **into internal jugular veins

Question 4

Meninges:

Arachnoid mater

Answer 4

Arachnoid mater = middle thin and wispy layer

**subdural space – between dura and arachnoid mater and contains small amount of serous fluid

Question 5

Meninges:

Pia mater

Answer 5

Pia mater = deepest layer tightly bound to surface of brain

**subarachnoid space – between arachnoid and pia maters – contains blood vessels and cerebrospinal fluid

Question 6

Meningitis

Answer 6

Meningitis = inflammation of the meninges from bacteria or virus – if spread to CNS can produce encephalitis - brain inflammation

Question 7

Ventricles

Answer 7

Ventricles
• continuous with one another = tubes that contain cerebrospinal fluid and lined with ependymal cells

• Lateral ventricle
• Third ventricle
• Fourth ventricle

Question 8

Lateral ventricle

Answer 8

*Lateral ventricle = relatively large cavities – one within each hemisphere of cerebrum
fuse with together in midline just inferior to corpus callosum

Question 9

Ventricles:

Third ventricle

Answer 9

*Third ventricle = small cavity in center of diecephalon between two halves of thalamus
cerebral aqueduct – passes through midbrain and connects third ventricle to fourth ventricle

Question 10

Fourth ventricle

Answer 10

*Fourth ventricle = within inferior portion of pons and superior portion of medulla oblongata
continuous with subarachnoid space
continues into spinal cord as central canal

Question 11

Cerebral Spinal Fluid (CSF)

Answer 11

Cerebral Spinal Fluid (CSF)
clear fluid similar to blood serum with most of proteins removed
provides protective cushion around CNS and allows brain to float within cranial cavity
provides some nutrients to CNS tissues
produced by **choroid plexus = in the roof of each ventricle - specialized ependymal cells, support tissue and associated blood vessels
fills ventricles, subarachnoid space and central canal of spinal cord
some drains into dura sinuses to be removed by venous circulation

Question 12

Blood Supply

Answer 12

brain has high metabolic rate and brain neurons not capable of storing high-energy molecules (glycogen)
requires large, constant blood flow for oxygen and glucose delivery
receives 15-20% of blood pumped by heart
interruption of blood flow for seconds can cause unconsciousness – for minutes = irreversible brain damage
blood-brain barrier = tight junctions between capillary endothelial cells, relatively thick basal lamina and astrocytes – maintains brain’s stable environment

Question 13

Cerebral Hemispheres:

superior and largest portion of the brain - size related to body size

Answer 13

Cerebral Hemispheres:

* *longitudinal fissure – separates cerebrum into right and left hemispheres
* *gyri = folds (ridges) on cerebral cortex – increases surface area
* *sulci = grooves between gyri

Question 14

Cerebral Hemispheres

Answer 14

Each hemisphere divided into lobes named for overlying skull bones:

* *frontal lobe – voluntary motor function, motivation, aggression, sensation of smell, mood, personality and decision making
* *central sulcus – midway along length of brain – separately frontal and parietal lobes
* *parietal lobe – sensory information
* *parieto-occipital sulcus – separates parietal from occipital lobes
* *occipital lobe – visual information
* *temporal lobe – smell and hearing and important role in memory
* *lateral sulcus – separates temporal lobe from rest of cerebrum
* *insula – island deep within lateral fissure – taste information

Question 15

Cerebral Hemispheres

Answer 15

• *grey matter
  
  • *cerebral cortex – on surface of cerebrum - up to 6 layers thick
  • *basal nuclei – islands of matter deep within the medulla
  **white matter- in cerebral medulla and contains tracts that connect areas of the cerebral cortex

Question 16

Cerebral Cortex

Answer 16

Cerebral Cortex
Nerve cell bodies, dendrites, glial cells and blood vessels
Three functional areas: motor, sensory, and accessory areas
**association areas – help integrate and interpret information
**contralateral organization – each hemisphere processes sensory and motor functions for opposite side of body

Question 17

Cerebral Cortex:

Motor area

Answer 17

Motor areas – control voluntary movement – in posterior part of frontal lobe

**Primary motor cortex – located on precentral gyrus = ridge anterior to central sulcus
controls precise or skilled voluntary movements
contains pyramidal cells - axons form motor tracts
somatotopy – body highly mapped onto cortex
**motor homunculus - region needing greater control are disproportionally represented

**premotor cortex – anterior to precentral gyrus – helps plan movements – selects and sequences basic motor movements into more complex tasks

**Broca’s area – anterior and inferior to premotor area – usually only on the left hemisphere
motor speech area

Question 18

Cerebral Cortex:

Sensory areas

Answer 18

Sensory areas - in parietal, insular, temporal and occipital lobes
**Primary somatosensory cortex – located on postcentral gyrus - posterior to central sulcus
receive information from general (somatic) sensory receptors in skin and from proprioceptors (position detection receptors) in skeletal muscle, joints and tendons
sensory homunculus

*Somatosensory association cortex - posterior to primary somatosensory cortex
integrates sensory inputs to produce understanding of object being felt – size, texture, relationship of parts

**primary visual cortex – extreme posterior tip of occipital lobe and visual association areas surround it

**primary auditory cortex – superior margin of temporal lobe next to lateral sulcus

**vestibular (equilibrium) cortex – responsible for awareness of position of head in space – posterior part of insula and adjacent parietal cortex

**primary olfactory cortex – involved in smell perception - medial aspect of temporal lobe

**gustatory cortex – involved in taste perception – located in insula

**anterior association area = prefrontal cortex – most complex area – involved with intellect, complex learning abilities (cognition), recall, and personality
contains working memory for abstract ideas, judgement, reasoning, persistence and planning
lesions or tumors in this area cause mental and personality disorders

Question 19

Cerebral Cortex:

Association areas

Answer 19

• *association areas – help integrate and interpret information
  
  • *contralateral organization – each hemisphere processes sensory and motor functions for opposite side of body

Question 20

Cerebral dominance:

Answer 20

Cerebral dominance:
**left hemisphere – dominant side for control of language, math and logic

**right hemisphere – visual-spatial skills, intuition, emotion, artistic and musical skills

Question 21

Cerebral White Matter

Answer 21

Cerebral White Matter

**association fibers – connect areas of cerebral cortex within same hemisphere

**commissural fibers – connect one cerebral hemisphere to the other
corpus callosum = largest bundle

**projection fibers – connects cerebrum to other parts of brain and spinal cord – form internal capsule

Question 22

Basal Nuclei

Answer 22

Basal Nuclei
Group of functionally related nuclei located bilaterally in inferior cerebrum, diencephalon, and midbrain
Involved in controlling motor function

• *corpus striatum =collective name for nuclei within cerebrum
  
  • *caudate nucleus
  • *lentiform nucleus – subdivided into laterally-located putamen and medially located globus pallidus

**subthalamic nucleus – in diencephalon

Question 23

Diencephalon

Answer 23

Diencephalon
• between brainstem and cerebrum
• contains: thalamus, subthalamus, epithalamus and hypothalamus

Question 24

Diencephalon

Thalamus:

Answer 24

thalamus = largest part with two lateral portions connected in center - interthalamic adhesion
**surrounds third ventricle of brain
**receives all sensory input (except olfactory)
synapse in thalamus then **relayed to appropriate areas of cerebral cortex

Question 25

Diencephalon:

Epithalamus

Answer 25

Epithalamus – superior and posterior to thalamus – forms roof of third ventricle
**pineal gland – secretes melatonin - modulator of biorhythms and sleep-wake cycle

Question 26

Diencephalon:

Hypothalamus

Answer 26

Hypothalamus = most inferior portion
contains several nuclei and tracts
**mammillary bodies = bulges on ventral surface – involved in olfactory reflexes and emotional responses to odors
**infundibulum = stalk containing blood vessels and axons and connects to pituitary gland

Major functions associated with nuclei:

* *central controller of endocrine system – release hormones that have direct effects on tissues and releases hormones that control release of hormones from the pituitary
* *major coordinator of autonomic nervous system
* *emotions – center of limbic system – directly involved in stress-related and psychosomatic illnesses and in feelings of fear and rage
* *body temperature regulation and shivering reflex
* *food and water intake – hunger, thirst and satiety centers, swallowing reflex
* *sleep-wake cycle

Question 27

Limbic System

Answer 27

Limbic System
central role in basic survival functions, and interpreting sensory input and emotions
deep portions of the cerebrum that form a ring around the diencephalon
parts of cerebrum and diencephalon
cerebral cortical areas = **cingulate gyrus (inner surface of longitudinal fissure), and parahippocampal gyrus (medial side of temporal lobe)
**dentate gyrus of hippocampus
**amygdala (part of basal nuclei)
**olfactory cortex
**fornix – connects the hippocampus to thalamus and mammillary bodies of hypothalamus

Question 28

Brainstem:

Midbrain, Pons, and Medulla oblongata

Answer 28

Brainstem
connects the spinal cord to the brain
contains three anatomical subdivisions (superior to inferior):
**midbrain, pons, and medulla oblongata
**and one functional unit – the reticular formation that spans all three anatomical divisions
contains many reflex centers essential for survival

Question 29

Brainstem:

Midbrain

Answer 29

Midbrain – contains nuclei for cranial nerves III, IV, and V
Four nuclei form mounds on dorsal surface = **corpora quadrigemina
**superior colliculi – receive sensory input from visual, auditory and tactile sensory systems
involved in reflex movements of head, eyes and body toward stimulus
“startle reflex”, loud noise, bright light, acute pain
**inferior colliculi – involved in hearing

**Red nucleus – (appears pink due to blood flow) aids in unconscious regulation and coordination of motor activities

**Substantia nigra- (appears dark due to melanin granules) part of the basal nuclei system
involved in maintaining muscle tone and coordinating movement

Question 30

Brainstem:

Pons

Answer 30

Pons – relay information form the cerebrum to the cerebellum
nuclei for cranial nerves V, VI, VII and VIII
sleep center that initiates REM (rapid eye movement) sleep

Question 31

Brainstem:

Medulla oblongata

Answer 31

Medulla oblongata = most inferior (caudal) portion of brain
Contains sensory and motor tracts
**pyramids – prominent enlargements on anterior surface:
contain large descending motor tracts controlling skeletal muscle

Cranial nerve **nuclei = clusters of grey matter composed mostly of neuron cell bodies
**olives – protrude from anterior surface lateral and superior to pyramids
nuclei involved in balance, coordination, and modulation of sound from inner ear
serve as **centers for vital reflexes
cardiovascular – regulating heart rate and blood vessel diameter
respiratory – rate and depth of breathing, coughing, sneezing
hiccupping, swallowing and vomiting
nuclei for cranial nerves V, VII, IX, X, XI, and XII

Question 32

Brainstem:

Reticular formation

Answer 32

Reticular formation = diffuse system of nuclei scattered throughout length of brainstem
receives axons from large number of sources
modulates and controls many functions of the brainstem
controls state of alertness and consciousness – including sleep-wake cycle

Question 33

Cerebellum

Answer 33

Cerebellum
assists in planning of movement – especially the coordination
modifies on-going movement by coordinating the force, direction, and extent of muscle contraction to prevent overshooting movement, maintain posture, and allow smooth coordinated movement
attached to the posterior portion of the pons

Question 34

Cerebellum

Answer 34

Three parts:
**flocculonodular lobe = small inferior part – helps control balance and eye movements

**vermis = narrow central portion
together with medial portion of lateral hemispheres control posture, and allow smooth flowing movements

**lateral hemispheres (2) – participates with cerebral cortex to plan, practice and learn complex movements
divided by **primary fissure into anterior and posterior lobes

Question 35

Cerebellum

Answer 35

Grey matter
on **cortex (surface) – has ridges called **folia
contains several cell types (neurons): stellate, basket, granule, Golgi, and Purkinje
**Purkinje cells – largest, inhibitory and only cortical neurons that send axons to the cerebellar nuclei
mossy fibers = afferent axons that branch extensively within cerebellum
and in **deep cerebellar nuclei surrounded by white matter

White matter in medulla – resembles branching tree = **arbor vitae

Question 36

Cerebellum

Grey matter and white matter

Answer 36

Grey matter
on **cortex (surface) – has ridges called **folia
contains several cell types (neurons): stellate, basket, granule, Golgi, and Purkinje
**Purkinje cells – largest, inhibitory and only cortical neurons that send axons to the cerebellar nuclei
mossy fibers = afferent axons that branch extensively within cerebellum
and in **deep cerebellar nuclei surrounded by white matter

White matter in medulla – resembles branching tree = **arbor vitae