the central nervous system

POWERPOINT® LECTURE SLIDE PRESENTATIONby LYNN CIALDELLA, MA, MBA, The University of Texas at AustinAdditional Text by J Padilla exclusively for physiology at ECC

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

HUMAN PHYSIOLOGYAN INTEGRATED APPROACH FOURTH EDITION

DEE UNGLAUB SILVERTHORN

UNIT 2UNIT 2

PART A

9 The Central Nervous System


Emergent Properties

Emergent properties of neural networks: Inexplicable properties –the structural components

of a neuron cannot explain the complex responses produced during neural processing/integration

Neuron circuits – a single neuron cannot fully perform its function, thus its optimal performance has to be within a circuit

Plasticity- allows the brain to change from circuit to circuit depending on sensory input and past experience


Arrangement of Nervous System Pathways


Spinal Cord Protection


Neural Tissue: Metabolic Needs

Oxygen Passes freely across blood-brain barrier

Brain receives 15% of blood pumped by heart

Glucose Brain responsible for about half of body’s glucose

consumption

Membrane transporters move glucose from plasma into the brain interstitial fluid

Hypoglycemia leads to confusion, unconsciousness, and death


Spinal Cord: Overview

Central nervous system, posterior view

Figure 9-4a

The spinal cord has two enlargements and ends in the lumbar region. Spinal nerves are part of the PNS and carry both sensory and motor neuron fibers.

The spinal cord has two enlargements and ends in the lumbar region. Spinal nerves are part of the PNS and carry both sensory and motor neuron fibers.


Spinal Cord: Anatomy

Specialization in the spinal cord

Figure 9-7a



Figure 9-7b

Propriospinal tracts remain within the cordTracts carry information in only one direction along a specified path of interneuron connections.

Propriospinal tracts remain within the cordTracts carry information in only one direction along a specified path of interneuron connections.


Spinal Cord: Integrating Center

Figure 9-8

Simple reflexes can be integrated by the spinal cord without input from the brain

Simple reflexes can be integrated by the spinal cord without input from the brain

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 9-9d

Anatomy of the Brain

Oldest and most primitive region of the brain. Ascending and descending tracts pass through the brain stem.

Oldest and most primitive region of the brain. Ascending and descending tracts pass through the brain stem.


The Brain: The Brain Stem Divided into three regions- medulla oblongota, pons, and

midbrain

Each region contains cranial nerves & nuclei that control autonomic function

Many nuclei are associated with reticular formation- white fibers what interconnect different areas throughout the brain.

Medulla Oblongata- controls involuntary funtions and connects to spinal cord. Somatosensory (ascending) and corticospinal (descending)

tracts in white matter

Pyramids- area where the fibers cross over thus the many functions are controlled by the opposite side of the brain.


2. Reticular formation- These are clusters of neurons (white matter) that run through the core of the brainstem. Involved in maintaining the brain alert, arousal, and sleep. It also control visceral functions like heart rate & vomiting. A motor tract goes down the spinal cord and is involved in movement.

Reticular FormationReticular Formation


Cranial Nerves10 of 12 cranial nerves originate along brain stem.

Create flash cards for the nerves on table 9.1, be able to identify their location, origin & destination, function, type of information each nerve carries

10 of 12 cranial nerves originate along brain stem.

Create flash cards for the nerves on table 9.1, be able to identify their location, origin & destination, function, type of information each nerve carries


Mid-sagittal View of the Brain


The Brain: Diencephalon

Figure 9-10

Thalamus is a relay and integrating station

Hypothalamus is the homeostasis center and also controls behavior related to homeostasis

Two endocrine structures: pineal and pituitary gland.

Thalamus is a relay and integrating station

Hypothalamus is the homeostasis center and also controls behavior related to homeostasis

Two endocrine structures: pineal and pituitary gland.


The Brain: Hypothalamus

The hypothalumus contains many nuclei that focus on the specific functions listed here.

Make flashcards of the info on this table

The hypothalumus contains many nuclei that focus on the specific functions listed here.

Make flashcards of the info on this table


The Brain: Cerebellum

Lateral view of brain

The cerebellum coordinates movement- also processes sensory information and motor input from the cerebrum; it smoothes and coordinates movement.

Figure 9-9b

Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 9-9c

Cerebral Mid-Sagittal View

Corpus Callosum is white matter that connects the two hemispheres

Sulci= groovesGyri= convolutions

Corpus Callosum is white matter that connects the two hemispheres

Sulci= groovesGyri= convolutions


White Matter in the cerebrum contains fibers that connect various brain areas


Gray Matter of the Cerebrum

Figure 9-11

Cerebral cortex is 30 layers thick and it’s the site of higher brain function.

The level of processing is directly related to the surface area

Basal ganglia- neural calculators that control movement

Cerebral cortex is 30 layers thick and it’s the site of higher brain function.

The level of processing is directly related to the surface area

Basal ganglia- neural calculators that control movement


The Brain: The Limbic System

Emotion, memory, learning, and visceral responses

Links higher cognitive functions and primitive emotional responses

Incorporates sensory areas, basal ganglia, and the diencephalon (hypothalamus) relates state of mind to physiological functions

Figure 9-13


Brain Function: complex processing and responses

The brain may generate information and output signals in the absence of external input

Motor output is influenced by sensory information, cognition, and behavior. Thus cognitive input may influence the motor output sent without sensory input.


Brain Function: Functional Areas of the Cerebral Cortex

Figure 9-15

Specialized sensations have separate designated areas on the cortexSpecialized sensations have separate designated areas on the cortex


Brain Function: Cerebral Cortex Three specializations – Sensory, Motor, and Association (cognition

and behavior). Sensory areas - stimulus activates sensory receptors, info travels in

ascending pathways and stops at the cerebellum or sensory areas of cerebrum

Sensory input translated into perception – brain’s interpretation of various input regions

Motor areas – info travels in descending pathways, cross-over at brainstem or spinal cord, and reaches muscles or glands

Direct skeletal muscle movement – initiated by cognitive system based on input from cerebral motoer ares, cerebellum, & basal ganglia

Association areas -

Integrate information from sensory and motor areas -

Can direct voluntary behaviors – control over conscious actions


Specialized Areas of the Cerebral Cortex


Body map along the Precentral and Postcental Gyrus


Brain Function: Sensory Information

Primary somatic sensory cortex- found on the post-central gyrus (parietal lobe) Skin, musculoskeletal system, and viscera-

components that send information to this region when a stimulus activates a sensory receptor

Somatosensory pathways – carry information of senses in conscious awareness of general somatic sense, damaged in brain area causes reduced sensitivity in opposite side Touch Temperature Pain Itch Body position


Brain Function: Sensory Information

Special senses have devoted regions -

Visual cortex –Occipital lobe (Visual Assosiaction area and Visual cortex)

Auditory cortex – Temporal lobe (Auditory association area and Audiotory Cortex

Olfactory cortex- Temporal lobe (uncus)

Gustatory cortex – Frontal lobe

Processed into perception – allows the stimulus to be translated into a different aspect (photons=colors) and “fills-in” missing information. Perception is the brains interpretation of sensory input and it is not directly dictated by the input


Brain Function: Motor Output Three major types

Skeletal muscle movement

Somatic motor division, involves voluntary actions processed at cerebrum or reflexes processed at the spinal cord

Neuroendocrine signals

Hypothalamus and adrenal medulla- secrete neurohormones that influence motor output

Visceral responses

Autonomic division- brains stem and diecephalon stimulate involuntary muscle and glands to maintain involuntary actions needed for function of internal organs and homeostasis

Voluntary movement Primary motor cortex and motor association- contralateral control, also

influence by behavioral and cognitive system


Brain Function: Cerebral LateralizationEach lobe has special functions- these are not equally shared

by the opposite lobe. Right handed people tend to have left hemisphere dominance.

Figure 9-16


Brain Function Influenced by Behavioral State Modulator of sensory and cognitive processes – incorporates the

reticular formation, hypothalamus, limbic system, and regions of the cerebral cortex

Neurons known as diffuse modulatory systems- regulate brain function by affecting attention, motivation, wakefulness, memory, motor control, mood, and metabolic homeostasis In reticular formation in brain stem- most originate at brain stem and

innervate areas of the cerebrum and diencephalon, classified by neurotransmitters used

Four modulatory systems Adrenergic – secretes norepinephrine, originate at pons, modulate:

attention, arousal, sleep-wake cycles, learning, memory, anxiety, pain, and mood.

Serotonergic – secretes serotonin, originate at brain stem midline, modulate pain, movement, sleep-wake cycles, mood, emotion

Dopaminergic – secretes domamine, originate at midbrain, modulate motor control and addictive behaviors

Cholinergic – secrete acetylcholine, originate at cerebrum and brain stem, modulate sensory information pathways through thalamus, arousal, sleep-wake cycles, learning, memory


Reticular Formation Pathways for Behavior Systems and Corresponding Neurotransmitters

See table 9-3 for information on neurotransmitter function


Behavioral State System: Arousal and Sleep-Wake Cycles

Consciousness- a state of arousal in which the brain is aware of self and environment Reticular formation- actively interacting through ascending tracts

Anesthetics- block signals from reaching the reticular formation

Electroencephalograms (EGG) Dectect level of activity of cerebral cortex neurons used electrodes

Awake State- various stage of awareness Uncoordinate firing of cortical neurons due to ascending signals in

reticular formation results in low-amplitude high-frequency waves

As awareness declines signals the frequency of waves declines and amplitute increases

Sleep- major rest period for the body, no external interaction, easily reversible, brain is as active as when awake, sleep inducing factors also boost immunity


Behavioral State System: States of Arousal

Electroencephalograms (EEGs) and the sleep cycle

Wave frequency lessens and amplitude increaes as arousal diminshes

During sleep the brain cycles multiple types between all stages

Delta waves are high amplitude, low frequency

Figure 9-20a


Behavioral State System: States of Arousal

Four stages with two major phases Slow-wave sleep – delta waves,

Adjust body without conscious commands

REM sleep

Brain activity inhibits motor neurons to skeletal muscle, paralyzing them –also reducing homeostasis responses

Dreaming takes place

Circadian rhythm Suprachiasmatic nucleus- location of neurons that

signal light-dark cycle phases and responses


Behavioral State System: Emotion and Motivation

The link between emotions and physiological functions

The amygdala is the center of emotion in the brain

Stimulus to Cerebrum- creates perception, limbic creates emotion, cerebrum becomes aware of emotion while hypothalus stimulates multiple responses

Figure 9-21


Behavioral/Cognitive State : Motivation

Defined as internal signals that shape voluntary behavior (related to survival or emotions)

Some states known as drives create increased arousal, goal-oriented behavior, and disparate behavior to achieve the goal.

Works with autonomic and endocrine responses to maintain homeostasis

Motivated behaviors stop Satiety

Pleasure is related to addictive behaviors which can be changed if given a different motivation.


Behavioral State System: Moods

Similar to emotions but longer-lasting- related to sense of being, not purely psychological, related to sense of well-being and proper neurotransmitter function

Mood disorders Fourth leading cause of illness worldwide today Depression

Sleep and appetite disturbances Alteration of mood and libido Antidepressant drugs alter synaptic transmission –

allow a neurotransmitter to remain at the synapse longer, change the receptor, or the amount of NT released.


Cognitive State: Learning and Memory Learning has two broad types

Associative – links two stimuli or a stimulus to a behavior Nonassociative- change behavior due to repeated exposure

Habituation – do not respond to an irritant stimulus, filters out insignificant stimulus

Sensitization- enhanced response to irritant stimulus, helps avoid harmful stimuli

Memory has several types Short-term and long-term- combined by working memory,

consolidation turns short-term into long term. Changes in synaptic connections are required

Reflexive and declarative- requires unconscious (procedural) or conscious recall (infer, compare, evaluate). Declarative can become reflexive


Brain Function: Memory Processing

Memory is stored as memory traces

Figure 9-22


Brain Function: LanguageCerebral processing of spoken and visual language

Damage to Wernicke’s causes receptive aphasia- unable to understand spoken or visual information

Damage to Broca’s area causes expressive aphasia- can understand information but cannot speak or write in proper order, are aware of mistakes

Figure 9-23a

the central nervous system

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