EXAM 2 (Neuro, Hormone, Energy, Fatigue)

Major divisions of the Nervous system:

- Central nervous system (CNS)

- Peripheral Nervous system (PNS)

PNS splits into:

- Sensory (afferent)

- Motor (efferent)

Motor divides into:

- Somatic (voluntary)

- Autonomic (involuntary)

Autonomic divides FURTHER into

- sympathetic (fight or flight)

- parasympathetic (rest and digest)

Neuron regions:

- Cell body

- Dendrites

- Axon

Cell Body:

- contains nucleus

- cell processes radiate out

Dendrites:

- Handle receiver cell processes

- Carry impulses toward cell body

Axon:

- Handles sender cell processes

- has end branches, terminals and neurotransmitters

Electrical charge of cell

- -70 mV

- Na+ outside cell

- K+ inside cell

Depolarization

- cell goes from -70mV to 0mV

- Na+ floods into cell

- allows nerve impulses to travel

Hyperpolarization

- 0 mV to -90mV

- K+ leaves cell

- stops impulses from traveling

Absolute Refractory Period

- during depolarization

- neuron unable to respond to another stimulus

Relative Refractory Period

- During repolarization

- neuron only responds to very strong stimulus

Transmission of AP

Axon -> synapse -> dendrites

Transmission within synapse

- presynaptic cell -> synaptic cleft -> postsynaptic cell

- electrical -> chemical -> electrical

AP only moves in ___

one direction

Exercise causes ____ release and sensitivity to Ach

increased

Neurotransmitters:

- 50+ known or suspected

- trigger GPs on new cell

- small-molecule, rapid acting

- large molecule (neuropeptides), slow-acting

Major exercise governing neurotransmitters

- ACh: skeletal muscle and parasympathetic

- NE: sympathetic

Components of CNS

- Brain

- Spinal Cord

Components of brain for CNS

- cerebrum

- diencephalon

- cerebellum

- brain stem

cerebrum:

- left and right hemispheres

- connected by corpus callosum

cerebral cortex:

- outermost layer of cerebrum

- gray matter

- conscious brain

Four superficial lobes of cerebrum

- frontal: general intellect, motor control

- temporal: auditory input, interpretation

- parietal: general sensory input, interpretation

- occipital: visual input, interpretation

One central insular lobe of cerebrum

- insular: emotion, self-perception

Ex Phys Cerebrum Regions:

- primary motor cortex (frontal lobe)

- basal ganglia (cerebral white matter)

-primary sensory cortex (parietal lobe)

primary motor cortex

conscious control of skeletal muscle movement

Basal ganglia

- cluster of cell bodies deep in cerebral cortex

- initiation of sustained or repetitive movements

- walking, running, posture, muscle tone

Diencephalon Parts:

- thalamus

- hypothalamus

thalamus:

- major sensory relay center

- determines what we are consciously aware of

hypothalamus:

- maintains homeostasis

- neuroendocrine control

- i/o, sleep, vitals

Cerebellum:

- controls rapid, complex movements

- coordinates timing/sequence of movements

-receives input from primary motor cortex

Brain stem:

- info relay between brain and spinal cord

- midbrain, pons, medulla oblongata

- contains reticular formation and analgesia

reticular formation:

- coordinates skeletal muscle function and tone

- controls cardiovascular and respiratory function

analgesia:

- pain control system

- opioid substances modulate pain here

- releases beta-endorphin with exercise

spinal cord:

- continuous with medulla oblongata

- nerve fiber tracts allow for two-way conduction of impulses

Impulse types:

- ascending afferent (sensory)

- descending efferent (motor)

Peripheral Nervous System:

- connected to brain and spinal cord

- two major divisions of sensory (afferent) and motor (efferent)

PNS nerves:

- 12 pairs of cranial nerves

- 31 pairs of spinal nerves

sensory division:

- transmits info from periphery to brain

-major families of sensory receptors

mechanoreceptors

physical forces

Thermoreceptors

temperature

nociceptors

pain

photoreceptors

light

chemoreceptors

chemical stimuli

joint kinesthetic receptors

- sensitive to joint angles/rate of angle change

- sense joint position and movement

muscle spindles

- sensitive to muscle length/rate of change

- sense muscle stretch

golgi tendon organs

- are sensitive to tension in tendons

- sense strength of contraction

motor division:

- transmits info from brain to periphery

- made of autonomic and somatic subdivisions

Somatic:

- stimulates skeletal muscle activity

autonomic:

- control of involuntary internal functions (organs)

- exercise related vital regulation

- made of sympathetic and parasympathetic division

sympathetic:

- fight or flight

- stimulation increases many factors

sympathetic stimulation increases:

- vitals

- blood flow to muscles

- bronchodilation

- metabolic rate

- mental activity

parasympathetic:

- rest and digest

- opposes sympathetic effects

parasympathetic stimulation:

- increased digestion

- conservation of energy

- decreased heart rate

- decreased diameter of vessels and airways

sensory-motor integration steps:

- stimulus sensed by receptor

- sensory AP sent on afferent neurons to CNS

- CNS interprets info, sends response

- Motor AP sent on efferent neurons

- arrives at skeletal muscle and response occurs

What first takes in and integrates info

parietal lobe

complexity of integration ____ with ascent through CNS

increases

CNS ascension order

1. Spinal cord

2. Lower brain stem

3. Cerebellum

4. Thalamus

5. Cerebral cortex (primary sensory cortex)

movement complexity ____ with level of control from spinal cord to cerebral cortex

increases

Motor reflex:

- instant and programmed

- response is identical each time

- happens before conscious awareness

Muscle spindle

- specialized intramural muscle fiber

- innervated by gamma-motor neurons

- sensory receptors for muscle fiber stretch

Golgi Tendon Organ

- sensory receptors embedded in tendon

- sensitive to tension in tendon

- important in resistance exercises

Motor Response

- alpha-motor neuron carries AP to muscle

- AP spreads to muscle fibers of motor unit

- fiber type is homogenous in a motor unit (type I OR type II)

Endocrine System

- communication system

- chemical communication

-slower to respond but longer lasting than nervous

- maintains homeostasis via hormones

Endocrine for exercise

- coordinates integration of physiological systems during rest and exercise

- controls substrate metabolism

- regulates fluid and electrolyte balance

Hormones: Steroid

- derived from cholesterol

- lipid-soluble, diffuse through membranes

- secreted by four major glands

Steroid four major glands

- adrenal cortex (cortisol, aldosterone)

- ovaries (estrogen, progesterone)

- testes (testosterone)

- placenta (estrogen, progesterone)

Hormones: Nonsteroid

- not lipid soluble, unable to cross membranes

- Two groups: protein/peptide or amino acid derived

Protein or Peptide Nonsteroid

- most nonsteroid hormones

- from pancreas, hypothalamus, pituitary gland

Amino Acid Derived Nonsteroid

- thyroid hormones (T3, T4)

- adrenal medulla hormones (EPN/NE)

Hormone Secretion

- secretes in brief bursts (pulsatile)

- plasma concentrations fluctuate over minutes/hours/days/weeks

-regulated by negative feedback

Plasma Concentration

- poor indicator of hormone activity

- cells change sensitivity and # of receptors

- downregulation = desensitization

- upregulation = sensitization

Hormone Receptors

- Controls scope of hormone effect

- typical cell has 2,000 to 10,000 receptors

- Hormone bound to receptor creates hormone-receptor complex (hrc)

Steroid Receptors

- found in cell cytoplasm or nucleus

- hrc enters nucleus, binds to DNA, regulates mRNA

Nonsteroid Receptors

- receptors on cell membrane send signal to second messengers

Common Second Messengers

- cyclic adenosine monophosphate (cAMP)

- cyclic guanine monophosphate (cGMP)

Prostaglandins

- third class of (pseudo)hormones

- derived from arachidonic acid

- act as local hormones (autocrines)

Prostaglandin Effects

- exert effects in immediate area

- mediate inflammatory response (swelling, vasodilation)

- sensitize free nerve endings (pain)

Major Endocrine Glands Responsible for Metabolic Regulation

- anterior pituitary gland

- thyroid gland

- adrenal gland

- pancreas

Anterior Pituitary Gland

- attached to inferior hypothalamus

- secretes hormones in response to hypothalamic hormone factors (both releasing and inhibiting factors)

- exercise increases secretion

Main Anterior Pituitary Gland Hormones

- growth hormone (GH)

- thyroid-stimulating hormone (TSH)

Growth Hormone

- potent anabolic hormone

- builds tissues and organs

- promotes muscle growth (hypertrophy)

- stimulates fat metabolism

- released proportionally to exercise intensity

Thyroid-Stimulating Hormone

- travels to thyroid, stimulus T3 and T4 release

- exercise increases TSH release

Exercise and TSH Release

- short term: T4 increases (delayed release)

- prolonged exercise: T4 is constant, T3 decreases

Thyroid Gland

- secretes T3 and T4

- T3 and T4 lead to increase in many things

T3 and T4 Increase:

- metabolic rates of all tissues and glycolysis/gluconeogenesis

- protein synthesis

- number and size of mitochondria

- glucose uptake by cells

- FFA mobilization

Adrenal Medulla

- releases catecholamines (80% EPN & 20% NE)

- increased exercise leads to increased EPN and NE

Catecholamine Releases Increases

- cardio diagnostics

- glycogenolysis

- blood flow to skeletal muscle

- increased glucose and FFA release

Adrenal Cortex

- releases corticosteroids, most importantly Glucocorticoids

- Major glucocorticoid is cortisol

Cortisol

- stimulates gluconeogenesis

- increases FFA mobilization, protein catabolism

- acts as anti-inflammatory

Pancreas

- releases insulin and glucagon

- insulin: lowers blood glucose, counters hyperglycemia

- glucagon: raises blood glucose, counters hypoglycemia

Hormones released by adipose tissue and gut (respectively) and act through CNS to decrease glucose production

Leptin and GLP-1

Only substrate for brain metabolism

Glucose

Lipolysis is stimulated by ____ via lipase

- decreased insulin

- EPN and NE (stimulate lipolysis)

- cortisol and GH (increase lypolysis)

Skeletal muscle fibers release _____ which _____

- cytokines and myokines

- cross talk between exercising muscle and other tissues

During exercise, plasma volume decreases, causing _____

- increase in hydrostatic pressure

- decrease in plasma water content via sweating

- increased heart strain

- decreased blood pressure

Glands/organs that correct fluid imbalances:

- posterior pituitary gland

- adrenal cortex

- kidneys

Fluid Regulation: Posterior Pituitary

- secretes antidiuretic hormone (ADH), or "vasopressin", and oxytocin

ADH:

-only ADH is involved with exercise

- increases water reabsorption at kidneys

- less water in urine, antidiuresis