The Central Nervous System: Anatomy and Physiology Chapter 12

Binghamton University BIOL 251

The Central Nervous System (CNS)

composed of the brain and spinal cord

What are the functions of the CNS?

integration/interpretation of incoming sensory information and sending out a motor response to effector organs

What are the four regions of the brain?

Cerebrum, diencephalon, brain stem, and cerebellum

Gray matter

consists of dendrites, cell bodies, and axon terminals

What is the function of gray matter?

Where all synapses are found, which is where neurotransmitters release

White matter

Consists of myelinated axons

What is the function of white matter?

passes “messages” between different areas of gray matter, sends impulses

In the brain…

Gray matter is peripheral and white matter is central

Cerebral cortex

Outer layer of gray matter

In the brain stem…

scattered gray matter found within white matter

In spinal cord…

gray matter in butterfly pattern surrounded by white matter, with central canal found at the center of gray matter

Ventricles

chambers filled with cerebrospinal fluid

2 lateral ventricles

one in each cerebral hemisphere

Third ventricle

found in diencephalon

Fourth ventricle

found in hindbrain

connects to third ventricle via cerebral aqueduct

continuous with central canal of spinal cord

Cerebral hemispheres

forms the most superior portion of the brain, make up most of brain by mass and have a wrinkled appearance for more surface area

What are the three general regions of the cerebral hemispheres?

Cerebral cortex, white matter, and basal nuclei

Gyri

ridges of cerebral hemispheres

Sulci

shallow grooves

Longitudinal fissure

separates left and right cerebral hemispheres

Transverse cerebral fissure

separates the cerebral hemispheres from the cerebellum

Cerebral cortex

provides self-awareness, sensation, communication, memory, understanding/learning, initiation of voluntary movement

hemispheres are contralateral

Motor areas of cerebral cortex

control voluntary movement

Sensory areas of cerebral cortex

conscious awareness of sensations

Association areas

integrate diverse information by connecting previous experiences with new experiences to form memories

What structures make up the motor areas of the cerebral cortex?

primary motor cortex, premotor cortex, Broca’s area, and frontal eye field

primary motor cortex

allows for conscious control of skilled/precise voluntary movements

pyramidal cells

large neurons found in primary motor cortex, axons travel to spinal cord in corticospinal tracts and synapse stimulates motor neurons

motor homunculus

the body is represented spatially in the primary motor cortex of each hemisphere

the larger the body part, the more neurons are dedicated to that region of the body on the cortex

premotor cortex

helps plan movements by selecting and sequencing basic motor movements into more complex tasks (must communicate with primary motor cortex) and controls voluntary actions that depends on sensory feedback

frontal eye field

controls voluntary movement of the eyes

Broca’s area

directs muscles involved in speech production

becomes active as we prepare to speak or as we plan other voluntary motor activities

is only found on one side of the brain (left side for most people)

Broca’s aphasia

disordered sentence structure, repeating, halting

What are the structures that make up the sensory areas of the cerebral cortex?

primary somatosensory cortex, somatosensory association cortex, visual areas, auditory areas, vestibular cortex, olfactory cortex, gustatory cortex, and visceral sensory area

primary somatosensory cortex

receive information from the general sensory receptors

general

anything that is not a special sense

sensory homonculus

the body is represented spatially according to site of stimulus input

the larger the body part, the more neurons are dedicated to that area of the body on the cortex

delusional ownership

when neurons are destroyed so body thinks body part is not theirs

somatosensory association cortex

integrates sensory input relayed to it via primary somatosensory cortex

produces understanding of what is being felt (size, texture, relationship of its parts)

What are the visual areas of the cerebral cortex?

primary visual cortex and visual association area

What is the largest region of the cerebral cortex?

the visual areas

primary visual cortex

receives visual information that originates on the retina in the eye

visual association area

uses past visual experiences to interpret visual stimuli which allows us to recognize things

What are the auditory areas of the cerebral cortex?

primary auditory cortex and auditory association area

primary auditory cortex

interpretation of sound from inner ear as pitch, loudness, and location

auditory association area

permits perception of sound and stimulates and stores memories of sounds for reference

vestibular cortex

allows for conscious awareness of balance/orientation

primary olfactory cortex

conscious awareness of different odors

gustatory cortex

perception of taste stimuli

visceral sensory area

allows conscious perception of visceral sensations (visceral organs)

ex: if an organ is overstretched, eating too much, awareness of overfilled bladder

Lateralization

a division of labor exists between the two hemispheres

Cerebral dominance

one hemisphere “dominates” a particular task (usually in reference to language)

Left side of the brain

language abilities, math, logic

Right side of the brain

Visual-spatial skills, insightful, creative

Fiber tracts

connect the left and right side of the brain and can share information almost instantaneously and allows complete functional integration

cerebral white matter

lies deep to cortical gray matter and is responsible for communication in the CNS

Classification of cerebral white matter

association fibers, commissural fibers, projection fibers

association fibers

connect different areas of the same hemisphere

commissural fibers

connect corresponding areas of different hemispheres which allows hemispheres to function as a coordinated “team”

projection fibers

allows sensory information to reach cortex and motor output to leave cortex

Basal nuclei of cerebral cortex (basal ganglia)

deep to the white matter in each cerebral hemisphere and filters out incorrect or inappropriate responses relating to muscle movement and emotions and cognition

Diencephalon

Made up of thalamus, hypothalamus, and epithalamus

Thalamus

relays sensory information coming into the cerebral cortex

nuclei have a certain function and therefore project information to a specific part of the cortex

information is edited here → impulses with similar functions are grouped together and relayed to the appropriate part of cortex

What are functions is the thalamus responsible for?

Motor activities, cortical arousal (sleep/wake cycles), learning, memory

Hypothalamus

Main visceral control center in the body

What does the hypothalamus control?

1. controls autonomic nervous system

2. initiates physical response to emotion

3. regulates body temperature

4. regulates food intake

5. regulates water balance and thirst

6. regulate sleep-wake cycles

7. controls endocrine system function

Epithalamus

pineal gland (pineal body) secretes hormone melatonin which helps regulate the sleep-wake cycle

Brain stem

Provides rigidly programmed, automatic behaviors necessary for survival, provides pathway for fiber tracts running from higher brain centers to lower brain centers and spinal cord, and innervation of the head

The midbrain

Regulates motor movement, regulates hearing and vision, alertness, and temperature control

The pons

respiratory control, bladder control, swallowing, and most functions associated with attached cranial nerves

Medulla oblongata 😉

Cardiovascular center, respiratory center, regulation of vomiting, swallowing, coughing, and sneezing

Cardiovascular center

regulates heart rate and blood pressure

Respiratory center

controls respiratory rhythm, depth of breath

Cerebellum

receptors in the body relay information to the cerebellum about body position and where the body is in space

motor cortex sends information to cerebellum about intent to move

cerebellar cortex decides best way to execute movement → force, direction, and extent of muscle contraction

What are the effects of the cerebellum?

Allows smooth, coordinated movements required for everyday life

Where does the cerebellum receive information from?

The body and the primary motor cortex (intent to move)

Cerebellar hypoplasia

Less coordination because the cerebellum is smaller than usual

Sloppy movement, dizziness, uncurable

Functional brain systems

networks of neurons that span multiple regions of the brain and work together to accomplish one or more related tasks

What are the two functional brain systems?

The limbic system and the reticular formation

The Limbic System

The emotional brain containing the amygdala and the cingulate gyrus

Amygdala (Amygdaloid body)

response to perceived threats with fear or aggression (fight or flight)

Cingulate gyrus

expressing emotions through gestures, resolving mental conflicts during times of frustration (prevents reacting excessively), and causes emotional responses to smell

How is limbic system output relayed?

Through the hypothalamus which is the main visceral control center in the body

Psychosomatic illness

Illness with physical symptoms that result specifically from emotional causes

Prefrontal cortex

Controls intimate relationship between out thoughts are feelings so we react emotionally to things we consciously understand to be happening and are consciously aware of emotions

How does the limbic system interact with the prefrontal cortex?

The communication between them explains why emotions sometimes override logic or why reason can stop us from expressing emotion inappropriately

Reticular Activating System (RAS)

cluster of neurons in the brain that sends continuous stream of impulses to the cerebral cortex (cerebral cortex is kept alert and excitability is enhanced) and filters out repetitive, familiar, or weak signals (prevention of sensory overload)

Language

Left side of the brain is mostly responsible for understanding language along with Broca’s area and Wernicke’s area

Wernicke’s area

language comprehension, “speaking clearly”

What does the corresponding area from language of the right hemisphere do?

Understanding and interpreting nonverbal components of language and understanding emotional components of language

Memory

the storage and retrieval of information/past experiences

Short-term memory (STM/working memory)

stores small amounts of information for short periods of time

Long-term memory (LTM)

stores large amounts of information for longer periods of time

transfer from STM → LTM

Can we ever forget something that is stored in LTM?

Yes, there is no permanent memory but things forgotten in LTM can be easier to relearn

What factors are necessary for transfer from STM to LTM?

Emotional state, rehearsal, association, and automatic memory

Declarative memory

learning explicit information, involves ability to manipulate symbols and language

Nondeclarative memory

Memory acquired through repetition → difficult to “unlearn”

Usually based on performance rather than recollection

Muscle memory

What are forms of protection for the brain?

Skull, meninges, cerebrospinal fluid, and blood-brain barrier

Meninges

Membrane that surround and protect the brain by covering the CNS, protecting blood vessels around the CNS, contain CSF

What are the three layers of of connective tissue that make up meninges?

Dura mater, arachnoid mater, and pia mater