Exercise Physiology Exam 2 (Nervous and Endocrine Systems)

Exam September 29th!

Axon

The neurons transmitter

Conducts signal away from cell body

Dendrites

Receives signals from other neurons

Soma

Also called the cell body

Contains the nucleus

Ion distribution (RMP)

ETC crates a charged gradient

High concentration of K+ inside of neuron

• Move freely in and out of cell help maintain distrobution

High concentration of Na+ outside of neuron.

Inside is negative and outside is postive

How is RMP maintained?

Sodium Potassium Pump

• enzyme that pumps out 3 Na+ for every 2 K+ in

• Keeps RMP at -70mV (imbalance creates negative charge)

  • Negative because of proteins do not cross the membrane

• Cost ATP

Depolarization

The inside of the cell becomes less negative than the outside of the cell

Causes action potencial

Hyperpolarization

The inside of the cell becomes more negative than the resting membrane potential

Resistant to creating an action potential

Inhibitory potential

Reduces membrane potential lower than the RMP to make the cell less likely to fire an action potential.

Excretory potentical

Increases the RMP to increase the likelihood of an action potential

How are action potentials initiated?

Normal RMP → deplararization (15mV-20mV above RMP or threshold potential) → Threshold is met or exceeded → all-or-nothing → action potential

(Summation is the combination of several graded potentials)

All or Nothing response

When depolarization meets or exceeds threshold potential → action potential

rising RMP → voltage gated Na+ channels open → votage continues to rise until all Na+ channels open → RMP rises to a certain point (too high) → Na+ channels to close → K+ channels to open → ending of the action potential → repolarization (hyperpolarization → normal RMP)

Saltatory conduction

Action potential travels from one break in mylin to the next

“jumps” for faster conduction

action potential is 5-50 times faster in mylinated than unmylinated

Neuron size

Smaller: Easier to active but conduct slower (smaller and have more resistance)

Larger: Harder to activate but conduct faster (larger and have less resistance)

Myelin

A fatty substance that insulates nerve fibers and facilitates faster action potential conduction through saltatory conduction.

Steps of action potential

1. The resting state
2. Depolarization
3. Propagation of an action potential
4. Repolarization
5. Return to the resting state with the help of the sodium-
potassium pump

Synapse/ transmission

Impulse → pre-synaptic axon terminal → synaptic vesicals release nuerotransmitters → synaptic cleft → Nuerotranmistters bind postsynaptic receptors (adjacent neuron)

Can only be transmitted from dendrite to cell body

Neuromuscular junction

Synapse for muscles / motor neuron meets muscle

Motor neuron → neurotransmitters → synaptic cleft → bind receptors muscle cell

RMP more negative in muscle

Acetylchonline

Opens up sodium channels (excitatory in skeletal muscle)

Released form parasympathetic neurons

Can be inhibitory (stops sodium channels in heart)

Norepineohrine

Sympathetic nervous response

Inhibitory (exercise) or excitatory depending on the receptor

aids in the body's response to stress and exercise, increasing heart rate and blood flow.

Refractory period

Sodium gates close for a short period of time

Will NOT respond to further simulation and limits firing frequency

Nerve and muscle cells go through this

Time is takes for the muscle fiber to repolarize

Cerebellum

Controls movement and balance

Cerebrum

Fine adjustments and fine-tuning of motor movements

higher cognitive functions (including reasoning, emotion, and memory)

Brain Stem

Control of respiratory and cardiovascular systems

regulation of reflexes such as swallowing and heart rate.

connects the brain to the spinal cord.

Afferent

to the brain

Peripheral Nervous system

12 pairs of cranial nerves connected with the brain.
31 pairs of spinal nerves connected with the spinal cord.

• Sensory division: carries sensory information from the body via afferent fibers to the CNS.

• End in either SC or brain

• Motor division: transmits information from CNS via efferent fibers to target organs.

• Autonomic nervous system: controls involuntary internal functions.

Afferent Neuron Pathways Motor

Afferent neuron pathways carry sensory information from the body to the central nervous system

processes it and sends motor commands back out through efferent neurons to control movement.

efferent

from the brain

Afferent Neuron Pathways Sensory

carry sensory information from receptors in the body (like skin, muscles, and organs) to the brain and spinal cord for processing

allows the nervous system to detect stimuli such as touch, temperature, pain, and proprioception.

Efferent Neuron Pathways Motor

carry signals away from the brain to muscles and glands, enabling movement and response.

Afferent Neuron Pathways Sensory

carry sensory information from receptors in the body—like skin, muscles, and organs—toward the central nervous system for processing

allows the brain and spinal cord to detect and respond to stimuli such as touch, temperature, pain, and body position.

mechanoreceptors

respond to mechanical forces such as pressure, touch, vibration, or stretch

Thermoreceptors

respond to changes in temperature

Nocicreceptors

respond to painful stimuli

Photoreceptors

respond to light to allow vision.

Chemoreceptors

respond to chemical stimuli from foods, odors, and changes in blood concentrations

Muscle and nerve joint nerve endings

Kinesthetic receptors
Muscle spindle
Golgi tendon organ

Kinesthetic receptors

In joint capsules sense position and movement of joints

Muscle Spindle

sense how much a muscle is stretched

key role in proprioception, providing feedback to the nervous system about muscle length and changes in length.

Cause stretch/myotatic reflex

• Contraction of the muscle when it is stretched too hard, too fast, or both. (protect from tearing or straining)

Golgi Tendon Organ

detect tension of a muscle on its tendon, providing information about the strength of muscle contraction

Tension → relaxation

Causes relaxation reflex or inverse stretch reflex

• Too much tension on a muscle GTO’s will send signals to the spinal cord to cause the muscle to relax (ensure it does not tear or stain)

Fight-or-Flight response

Sympathetic nervous system

Increase in body functions to prepare the body for perceived threats, involving increased heart rate, blood pressure, and energy availability.

Actions that oppose the sympathetic system

• decrease heart rate

• Constricts coronary vessels

• Constricts tissues in the lungs

Target organs SNS during exercise

heart, blood vessels, bronchioles, respiratory muscles, skeletal muscles, adrenal medulla, pancreas, pupils, digestive tract

Prepare the body for danger by increasing heart rate, blood flow, and oxygen delivery while diverting blood from non-essential functions.

Target organs of PNS during exercise

Nerves, Heart, bronchioles (mild bronchoconstriction → low oxygen need), digestive, badder, reproductive organs

Helps the body relax

Suppressed during exercise but is simulated after to restore homeostasis

Motor control

Deliberate action

reflexes

Deliberate action

Reflexes

Actions of the muscle spindle

muscle contraction triggered resist further stretching

Muscles attached to spindle stretched neurons on spindle transmit info CNS (spinal cord) about muscle length

Middle of spindle dose not contract but stretches

Detect quick stretch → contraction (ensure muscle does not rip or tear)

Actions of the Golgi tendon

Detect changes in tension

Inhabit contracting (antagonist) muscles and excite antagonist muscles prevent injury

Smooth movements 

information to Spinal cord 

Conscious movement

primary motor cortex → voluntary muscle movements

Clusters of nerves in the basal ganglia initiate sustained repetitive movements

Cerebellum controls fast, complex muscular activities

Motor units and size principle (henneman’s size principle)

The number of motor units depends on the force needed/ produced

Recruits ST units (most fatigue resistant) then FT (Less fatigue resistant but more explosive)

• exceptions explosive movements

Engrams 

are the physical traces of memory in the brain, representing the storage of learned information and experiences.

Stored in pre-motor movements

• slower (sensory portion)

• Rapid movements (motor portion)

Nervous system

immediate response

immediate/short term effects

localized

endocrine system

slower response

longer lasting

more general effect

endocrine

ductless glands that secrete hormones directly into the bloodstream.

exocrine

glands that secrete hormones through ducts to target organs.

Sweat glands

Steroid hormones

made of lipid molecules

diffuse easily through cell membrane 

chem structure similar to cholesterol

secreted by the…….

• adrenal cortex: cortisol

• ovaries: estrogen 

• testes: testosterone 

• placenta: estrogen 

nonsteroid hormones

built of amino acids

Cannot diffuse through membranes

Bind to receptors on outside of cell to cause changes on inside of cell

• cause cascade (enzymes and secondary messengers) that leads to DNA activation and transcription and translation 

Two types

• amino acids derivatives: epinephrine 

• Protein/ peptide hormones: insulin 

prostaglandins (where they come from and what do they do?)

3rd class of pseudo hormones

Derived from arachidonic acid 

• fatty acid (part of cell membrane)

Act as local hormones (immediate area)

• inflammatory response (swelling, vasodilation)

• Sensitize nociceptor free nerve ending (pain)

Negative feedback

secretion of hormone causes change that inhibits further secretion of the hormone

key way to maintain homeostasis in the body.

Up regulation

Increase the number of cell receptors (more receptors for the hormone to bind to)

• lower concentration of hormone remains in blood plasma for enhancing hormone sensitivity and effectiveness.

Often times good 

down regulation

Decrease in cell receptors, reducing hormone sensitivity leading to higher hormone concentrations in blood plasma.

often times bad (type 2 diabetes)

Pituitary gland

relay between nervous system and endocrine systems

produces and secretes hormones regulating various bodily functions, including growth and metabolism depending on the signals from the nervous system and hypothalamus

Posterior pituitary 

Hormones

• Antidiuretic hormone

• Oxytocin

Controlled by nervous signals

Anterior pituitary

Hormones

• growth hormone

• thyrotropin 

• Luteinizing hormone

• Prolactin 

• Adrenocorticotropin 

Exercises increases all six hormones

4 tropic hormones

• control function of other glands

  • adrenal glands, gonads, thyroid

Other

• prolactin and GH

Growth hormone

promotes muscle growth and hypertrophy → amino acid transport

simulates breakdown of fat

levels elevated during aerobic exercise in proportion to exercise intensity

• higher the intensity more produced

Thyroid gland

Hormones

• T3 (triiodothyronine), T4 (thyroxine)

  • Increase metabolic rate 60-100%

    • increased protein. enzymes synthesis, size and number of mitochondria in cells. FFA availability for oxidation, promote rapid cellular uptake glucose, enhance glycolysis

    • increases secondary messengers in cells

  • Calcitonin

    • metabolizes calcium

      • not strong regulator in adults

Adrenal Medulla

• medulla (inner)

• cortex (outer part)

Hormones 

• catecholamines: epinephrine, norepinephrine 

  • stimulate sympathetic NS prepare for action 

  • Increase heart rate and force of heart contraction, blood pressure, reparation, metabolic rate (glycogenolisys, and release if glucose and FFA in blood)

  • allow more blood transported to skeletal muscles → vasodilation and vasoconstrictions

Adrenal cortex

Mineralocorticoids

• maintain electrolyte balance extracellular fluids

• Aldosterone → sodium retention → retain more water

Glucocorticoids

• Maintain contant plasma glucose levels between meals

• Cortisol: important stress hormone

Gonadocorticoids

• Released addition released by reproductive organs lesser amounts

• Androgens, estrogens, progesterones

Pancreas

Both endocrine and exocrine

Insulin (only hormone lowers blood glucose)

• secreted → plasma glucose elevated (hyperglycemia)

•  promotes glucose uptake cells (muscles + connective tissues)

• Promotes glycogenesis

• inhibits gluconeogenesis 

• Building and storing state

Glucagon 

• Secreted → plasma glucose lowered (hypoglycemia)

• Increases liver glycogenolysis 

• increases gluconeogenesis

• Raises blood glucose 

How training effects glucagon and insulin?

Up regulation for glucagon (have to release less hormone) 

• glucagon increases when exercises 

• Training increases the receptors for glucagon 

• Untrained higher glucagon levels then trained

Down regulation for insulin

• Insulin decreases when exercises

• Able to better target tissues that need glucose

• Training reduces the receptors for insulin 

  • increased cellular receptors for glucose

• increase sensitivity for glucose

• Untrained has lower insulin levels then trained

Androgens

Testosterone

male 2nd sex characteristics 

major anabolic hormone 

• stimulates muscle hypertrophy 

Estrogens

Female 2nd sex characteristics

muscle function

Progesterone

Prepares for pregnancy

Kidney

Erythropoietin: regulates red blood cell production (stimulates production of blood cells)

• Important for adaptation to training and to altitude due to the oxygen-carrying capacity of red blood cells

Major endocrine glands for metabolic regulation

anterior pituitary gland

thyroid gland

adrenal gland

pancreas

Hormones produced by these affect metabolism if carbs and fats during exercise

Hormones

Chemical messengers that travel in blood to regulate various physiological processes in the body.

Binds to specific receptors on cells (specific target organ)

• 2,000-10,000 receptors per cell

Can be released by non-endocrine tissues (nerve endings, adipose tissue)

Adequate glucose for exercise needs

glucose re-uptake by liver

glucose uptake by muscles

Increase circulating glucose metabolism (counter the effects of insulin)

• glucagon

• epinephrine 

• norepinephrine 

• cortisol 

Increase blood glucose

Circulating glucose during exercise affected by 

Growth hormone

• increases FFA mobilization, decreases cellular glucose uptak

T3 + T4

• increase glucose catabolism and fat metabolism

amount of glucose regulated from liver depends on exercise intensity and duration

As Exercise intensity increases…

catecholamine release increases

glycogenolysis rate increases (liver and muscles)

Muscle glycogen used before liver glycogen

As exercise duration increases….

more liver glycogen utilized

increase muscle glucose uptake → increase glucose release

as glycogen stores decrease, glucagon levels increase

Cortisol and exercise

Peaks during exercise, increases glucose availability then decreases as exercise progresses to longer durations

Insulin and carb metabolism during exercise

enables glucose uptake in muscle

During exercise

• insulin concentrations decrease

• cellular insulin sensitivity increases

• more glucose uptake into cells

  • use less insulin

FFA mobilization and fat metabolism endurance exercise preformance

glycogen depleted → fat energy substrates

• response → hormones accelerate fat breakdown (lipolysis)

Triglycerides → FFA + glycerol

• FFA transported → muscles

• rate of triglyceride breakdown → FFA may determine the rate of cellular fat metabolism

Lipolysis stimulated by…

Decreased insulin 

Epinephrine*

Norepinephrine*

Cortisol*

Growth hormone

(Stimulate lipolysis via lipase)

(can also promote glucose metabolism)

Hunger Hormones

Cholecytokinin (CCK): stimulated by full stomach (released by intestine)

Ghrelin: Triggered by empty stomach → hunger (secreted by pancreas)

Leptin: acts on the brain to suppress hunger (secreted by fat cells)

How renin, ADH, and aldosterone interact to maintain plasma volume

Renin: increases blood pressure and regulates blood volume, converts angioteninogen → angiotensin 1 → (by enzymes) angiotensin 2 (causes vasoconstriction → raises blood pressure)

• increases blood volume (sodium retention) and pressure

• Simulated by low blood pressure → loss of fluid

Aldosterone: Regulates fluid/electrolyte balance

• sodium retention → water retention → increases blood pressure and volume

Antidiuretic hormone/ vasopressin: fluid regulation

• increases water reabsorption from urine

• concentrate electrolytes in blood

• Increases blood osmolarity

How they work together: Renin released from kidneys response low blood pressure → Renin → angiotensin 1 → production angiotensin 2 → promotes secretion of aldosterone from adrenal glands + stimulates thirst/ production of ADH → Urine volume decreases. Regulate/maintain homeostatic plasma volume → controlling blood pressure + fluid balance

Osmolarity

is the measure of solute concentration in a solution, reflecting the number of osmoles of solute per liter of solvent. It plays a crucial role in fluid balance and the movement of water across cell membranes.

Hemoconcentration

highly concentrated blood

thick/ increased viscosity 

hard for heart to pump blood

Hemodilution 

Unconcentrated blood 

More fluid/ too much water

Low solutes

thin/ decreased viscosity