Test 2

Lecture 8 central nervous system(CNS)- part 2

Autonomic Motor System responsible for involuntary movement

- Neural pathways: a series of neurons connected by synapses that form a line of communication for a specific task

Automatic patterned response = reflex
Neural pathways for reflexes = reflex arc
Components of reflex arc - stimulus hits
1 sensory receptor → 2 afferent neuron → 3 Integrating center → 4 efferent neurons → 5 effector (organ muscle,gland)
Response occurs
4 classes of Reflexes

1. Spinal - Muscle spindle stretch reflex

Cranial - pupillary reflex

2. Somatic (voluntary) - Muscle spindle stretch reflex

Autonomic (involuntary) -baroreceptor to control blood pressure

3. Innate - Muscle spindle stretch reflex

Conditioned - salivation reflex of Pavlov’s dogs

4. Monosynaptic - Muscle spindle stretch reflex

Polysynaptic - all other reflexes

Muscle spindle stretch reflex

Spinal reflex
Only known monosynaptic reflex in the body
For leg extension, the stretch reflex triggers contraction of the quadriceps and inhibition of the hamstring

Withdrawal reflex - automatic reflex to painful stimulus

nociceptors
Crossed-extensor reflex - initiated simultaneously with the withdrawal reflex
eflexes can sometimes be overridden
– Brain activates inhibitory neurons in spinal
cord to suppress reflex
– PSPs sum so if inhibitory influence from brain
> excitatory influence from nociceptor →
withdrawal reflex inhibited

pupillary light reflex

autonomic, cranial reflex

• Innate reflex

• Polysynaptic reflex

• Reflex arc:– photoreceptors → afferent neurons

→ midbrain nuclei → efferent neurons → pupils

Somatic Motor System

Responsible for voluntary movement

Voluntary Motor control

4 components
idea, program, execution, feedback Involves

Idea

Limbic system
Association areas
Supplementary motor area

Program

Supplementary motor area
premotor area
Primary motor cortex

Execution

Pyramidal tract axons originate in primary
motor cortex and terminate in
ventral horn of spinal cord
• Called upper motor neurons
– Most cross to contralateral side in
medullary pyramids
– Also have collaterals that travel to
other motor areas
– Fine control of voluntary movement
of the distal extremities (especially
forearms, hands and fingers)
Extrapyramidal tract-All motor pathways outside
pyramidal tracts
– Support voluntary movement of
the proximal extremities
– Indirect input to motor neurons
– Several pathways
Motor neuron

Feedback

sensory system

cerebellum - critical for motor coordination, provides feedback control of motor function, contributes to muscle tone, stores programs for remembered activities

thalamus
Basal nuclei

Basal Nuclei in Motor control

Functions similar to cerebellum
• Feedback control of voluntary movements
• Select purposeful over unwanted movements
• Damage can result in
– Huntington's chorea fast movement
• Genetic disorder of basal nuclei
• Pathway from basal nuclei to thalamus is lost
– Parkinson's disease mid brain dopamine often associated with slow movement
• Disease of basal nuclei -
• Lack of dopamine in substantia nigra (inhibitory area of midbrain)

Brainstem

ALL lead to muscle contraction and movement

Language sleep learning and memory

wernicke’s area

Language comprehension

• Wernicke's aphasia

– Difficulty understanding both

written and spoken language

– Can speak words but they make

no sense

Broca’s area

Language expression

• Broca's aphasia

– Can comprehend and know what want

to say but cannot make correct sounds

or write the words

Sleep- study of sleep

Active process

• Theories on purpose of sleep

– Lets body rest

– Lets brain rest

– Enhances memory

– Enhances learning

– Supports adequate immune system function

– A time delay of about 3 hours after learning before sleeping improves

declarative memory consolidation

– May prevent the buildup of abnormal proteins found in Alzheimer’s

Disease.

Electroencephalogram (EEG): Electrodes on the

scalp detect synaptic potentials produced by cell

bodies and dendrites in the cerebral cortex. Four

patterns for adults are usually seen:

1. Alpha waves: awake, relaxed brain with eyes closed;

most in parietal and occipital lobes

2. Beta waves: produced with visual stimulation and mental

activity; seen most in frontal lobe; evoked activity

3. Theta waves: found in sleeping adults and newborns;

increase when awake doing tasks that require attention

and memory, during sleep deprivation and severe

emotional stress; most from occipital and temporal lobes

4. Delta waves: seen in sleep and an awake infant, from all

over the cerebrum; indicates brain damage if seen from

an awake adult

May be genetically controlled, although sleep is affected by environmental

factors

• Neurotransmitters involved

1) Histamine and other NTs – wakefulness

2) Adenosine & GABA – sleep

Two recognized categories:

1) REM: rapid eye movement; state when dreams occur; EEG shows theta

waves

2) Non-REM: also called resting sleep; divided into four stages, determined

by EEG waves seen. Stages 3 and 4 are often called slow-wave sleep,

characterized by delta waves.

Sleep-Wake Cycles

• Ascending reticular activating system (ARAS)

– Critical in maintaining alert wakefulness

– Part of reticular formation

– Projections to thalamus, hypothalamus, and

forebrain

• Forebrain: induces slow-wave sleep (SWS)

leep-Wake Neurotransmitters

Awake state

– Acetylcholine

• ARAS

• Mimicked by nicotine

– Norepinephrine and

dopamine

• ARAS

• Mimicked by

amphetamines and

cocaine

Sleep state

– Adenosine

• SWS induced by forebrain

• Blocked by caffeine

– Acetylcholine

• REM sleep

• Pons

Sleep – EEG Waves

• Awake (alert) – beta waves

– Generated by many neurons at different times

• Awake (resting) – alpha waves

– More synchronization of electrical activity

• Stage 1 Sleep

– Lightest sleep i.e. lowest arousal threshold

• Stage 2 Sleep

– light sleep

• Stage 3 Sleep

– moderate sleep

• Stage 4 Sleep

– deep sleep i.e. highest arousal threshold

• REM Sleep

Learning and Memory

Learning

– Acquisition of new information

– Hippocampus is important

Associative learning

– making connections between two (or more) stimuli

Non-associative learning

– Habituation

– Sensitization

Whether you become habituated or sensitized to a stimulus depends on circumstance – if

perceive stimulus to be important become sensitized, if unimportant, habituated

Memory

– Retention of information, skills, or thoughts

Memory Processes

Procedural memory = implicit

– Learned motor skills and behaviors

– Automatic response: does not require a conscious effort

– Cerebellum is involved

Declarative memory = explicit

– Learned facts, events, and experiences

– Requires conscious effort for recall

– Hippocampus is involved

Short-Term and Long-Term Memory

• Information is first stored as short-term (working)

memory

– Lasts seconds to hours

– Information is lost unless consolidated

– Frontal lobe is critical for short-term memory

• Consolidation from short-term memory to long-term

memory

– Mechanism unknown

• Long-term memory

– Lasts years to lifetime

– Temporal lobe and hippocampus important

Plasticity in the Nervous System

• Learning and memory involve plasticity= limited ability to

alter anatomy and function in response to changes in

activity patterns

– Development of new synapses

– Long-term modulation of existing synapses

– Recently shown new neurons develop

– One example of plasticity = long term potentiation (LTP)

• LTP = repetitive stimulation of a particular synapse leads to increase in strength of the synaptic connection i.e. increases likelihood that AP will be triggered in postsynaptic cell

• Increases in synaptic strength occur because of increase

in size of EPSPs generated in post synaptic cell

Plasticity in the Nervous System

Increase in sensitivity of
postsynaptic cell can be due
to increased sensitivity to NT
released at that synapse,
increase in amount of NT
released or both
Glutamate
receptors AMPA
and NMDA are
agonist

Exercise and the Brain

• Research indicates

that exercise enhances brain

activity

– Aerobic exercise in the elderly can improve cognitive

function and slow dementia in Alzheimer’s patients

– Can also improve mood disorders at any age

– How?

• Possibly exercises enhances metabolic activity of brain

• Increased blood flow to brain which may enhance brain

activity and decrease brain deterioration

Lecture 11: immune system

Immunity

Immune response - recognition and elimination of pathogenic agents

Disposal - Aging cells, cellular debris from diseased tissue, sometimes mutant cells

wound healing

Anatomy of the immune system

Physical barriers -

skin - tightly packed cell arranged in layers

mucous membranes - form a continuous barrier with skin. Produce viscous mucus or acid (GI tract)

Leukocytes- white blood cells, wide range of immune response

Granulocytes-With cytoplasmic granules containing secretory products- release via degranulation

Agranulocytes - no granules
Phagocytes - engulf foreign particles and microorganisms and remove them from blood or tissue; neutrophils, eosinophils, and monocytes being in blood and neutrophils being most abundant, while macrophages were in tissue as well dendritic cells
Lymphocytes - 3 major types
Lymphoid tissues - Central, Peripheral

Central lymphoid tissue → Bone marrow, thymus, fetal liver

Peripheral lymphoid tissue → spleen, lymph nodes, tonsils, adenoids, lymph nodules of GI tract

B lymphocytes - When they contact antigens (foreign particle or abnormal molecule) and tag foreign entities for destruction , contacts antigen plasma cells secrete antibodies ( or immunoglobulins)

T lymphocytes- Do direct damage to foreign or abnormal cells (infected, mutant or transplanted cells) contact infectecell and days later cytotoxic t cell secretes and creates pores in target cell’s membrane causing the cell to fill ith fluid and cell lysis

Natural Killer- important in fighting viral infections make up a small amount of lymphocytes; similar mechanism to T cells but recognize cells differently, show immediate readiness-→ fast response compared to B and T cells, operate early and nonspecifically perforins are secreted causing cell lysis part of innate and also specific response

Can undergo clonal expansion and display increased cytotoxicity to

repeat antigens

Inflammation -Interferons

– Prevents spread of viruses in body

• Interferes with viral replication

– Proteins secreted by leukocytes and virus-infected cells =

interferon-α and interferon-β

Virus infected cell

accumulates viral

nucleic acid

Healthy

cell

Healthy

cell

Healthy

cell

Interferon synthesized and

secreted

Host cell usually

dies

Healthy cells resistant

How?

• RNA degrading

enzymes

• Protein synthesis

inhibitors

• Block production of

new viruses

Nonspecific Defenses- Activation of innate

immunity

BIOL2010 Human Physiology

Interferons (Cont’d)

– Interferon-γ

• Secreted from active T cells and NK cells

• Inhibits viral replication

• Enhances phagocytosis by macrophages

• Boosts antibody production in B cells

• Helps activate NK cells and cytotoxic T cells

• Inhibits cell division—defense against cancer

Nonspecific Defenses- Activation of innate

immunity

BIOL2010 Human Physiology

Complement system

– Can act specifically or non-specifically depending on

whether antibodies are present

• Completes actions of specific antibodies

– Consists of 30 plasma proteins that destroy invading

microorganisms especially bacteria

– Complement cascade can be activated in three ways…

Nonspecific Defenses- Activation of innate

immunity

BIOL2010 Human Physiology

Complement system (Cont’d)

Antibody binding

Binding of serum protein (Lectin)

to bacteria

Direct binding of

complement

protein to carbs

on surface of

bacterial cells

Nonspecific Defenses- Activation of innate

immunity

Figure 23.7 (Pearson) | Complement activation and actions

BIOL2010 Human Physiology

• Depends on

presence of

antibodies

• Proteins: C1 – C9

• Non-specific, fast compared to classical

pathway; does not rely on production of

antibodies

• Lectins bind specific carbs

• MBL = mannose binding lectin

• Non-specific, fast

compared to classical

pathway; does not

rely on production of

antibodies

• Activates at point

further along than

classical i.e. at C3

Complement system (Cont’d)

Nonspecific Defenses- Activation of innate

immunity

Figure 23.8 (Pearson) | Complement pathways

BIOL2010 Human Physiology 30

Details of MAC (Membrane Attack Complex

Layers of Defense

Physical – skin, mucous membranes, mucus and other secretions

Chemical – enzymes, antibodies, pH

Non-specific (innate) Immune Response

Rapid, non-specific, no memory

Cells – macrophages*, neutrophils, NK cells, dendritic cells*, eosinophils, basophils

Chemical – complement system, interferons

Specific (adaptive) Immune Response

Slow, specific, memory

Humoral immunity and Cell-mediated responses – B cells (plasma cells), T cells

(cytotoxic T, Helper, Regulatory T cells)

Antibody-mediated responses – antibodies

Pathogen destruction/suppression

Defense Mechanisms - 2 types: innate, adaptive

Innate (nonspecific) immunity – inherited; includes
physical barriers, phagocytosis, and more; trained
immunity – cells that show increased effectiveness
during a second exposure to a pathogen that may be
due to epigenetic cell changes
Adaptive (specific) immunity – learned from exposure
to specific pathogens (immunological memory); function
of lymphocytes and antigens

Virus,bacterium parasite and fungi activate immune system

Nonspecific Defenses- Activation of innate

immunity

• Fast protection, recognition of pathogen but non-specific

• Cells distinguish “self” from “non-self” via pathogen-associated molecular

patterns (PAMPs) unique to the pathogens

– Pattern recognition receptors (PRRs) on immune cells bind to PAMPs to initiate the

innate immune response

– Examples of PAMPs include:

1) Includes lipopolysaccharides (LPS) found in the envelop of Gram-negative bacteria

2) Peptidoglycan from the cell walls of Gram-positive bacteria

• Non-specific defenses include:

1. Physical barriers (previously covered, slide 6)

2. Inflammation

3. Interferons

4. Complement system

Lecture 9 Muscle Physiology

Muscles

There are 3 muscle types smooth cardiac a skeletal
Muscles like neurons are excitable tissues
Action potentials induce contractions to generate force→movement occurs

Skeletal muscle

Tendons -connective tissue that transmit
force from the muscle to the bone.
Muscles are connected to bone via
tendons
Fascicles -bundles of individual
muscle cells. Each fascicle
contains thousands of muscle
cells, called muscle fibers
perimysium - connective
tissue. Divides the body into
numerous bundles of
individual muscle cells
(fascicles)
endomysium thin connective
tissue covering each muscle fiber
Epimysium - connective
tissue surrounding the
muscle tissue

Structure at the Cellular Level

muscle fiber or fascicles components

multiucleated
sarcolemma - plasma membrane
sarcoplam - cytoplam
mitochondria Myofibrils
arcoplasmic reticulum (SR)
• Surrounds each myofibril
• Associates with T-Tubules
• Near the T-tubules, the SR has regions
called, Lateral sacs/terminal cisternae
= store calcium
– Transverse tubules (T-tubules) – run
continuous with the sarcolemma and
plays a role in muscle contraction
components of a muscle fiber (Cont’d)
– Note relationship between sarcolemma and T-tubule
– Note relationship between SR and terminal cisternae
– Triad = one T-
tubule and two
terminal cisternae
(lateral sacs)
Functions:
– Sarcoplasmic reticulum (SR) and transverse tubules (T-
tubules) are important in activation of muscle contractions
• Transmit signals from sarcolemma to myofibrils
– Sarcoplasmic reticulum and terminal cisternae
• Store Ca2+
• SR membrane has calcium pumps
– Active transport of calcium ions into SR
– Cytoplasmic levels of calcium normally low due to pumps

Motor units & Somatic neurons

• A motor unit = one somatic motor neuron +

all the muscle fibers it innervates

• Functional Principle:

• When a motor neuron is activated, all

muscle fibers in its motor unit

contract simultaneously

• The cell body of a somatic motor

neuron is located in the ventral

horn of the spinal cord gray matter.

• A single axon exits via the ventral

root of a spinal nerve.

• The axon branches into multiple

collateral fibers, each innervating

a different muscle fiber.

Neuromuscular Junction & Muscle Fiber Activation

Each muscle fiber is

innervated by a single somatic

motor neuron via a synaptic

bouton.

• The neuron releases

acetylcholine (ACh) at

the neuromuscular

junction (NMJ).

• ACh binds to receptors

on the motor end plate

(specialized region of the

sarcolemma).

Motor End Plate Structure:

• Deep folds increase surface area

• Crests: high density of ACh

receptors

• Troughs: rich in voltage-gated Na⁺

channel

Structure at the molecular level

Myofibrils

– Contain protein fibers

• Thick filaments -myosin

• Thin filaments - actin

2(thin):1(thick) ratio

Orderly arrangement

of thick and thin

filaments give skeletal

and cardiac muscle

striated appearance

Structure of Sarcomere at the

Molecular Level