Study guide: Human Physiology and Nervous System

📋 Course Outline

1. Feedback Mechanisms
2. Kidney Function and Urine Formation
3. Kidney Regulation of Homeostasis
4. Reproductive Hormones and Aging
5. Neurons and Nerve Impulses
6. Synapses and Neurotransmitters
7. Drugs and Neural Signaling
8. Brain Regions and Functions
9. Spinal Cord and Reflexes
10. Peripheral Nervous System Divisions

📖 1. Feedback Mechanisms

🔑 Key Concepts & Definitions

• Negative feedback: A mechanism in which the final product of a reaction slows or stops the activity of the enzyme that started the reaction.
• Positive feedback: Positive feedback occurs when the final product of a process further increases that same process.
• Predictive feedback: Predictive feedback occurs when the body anticipates a change and acts in advance to prepare for it.

📝 Essential Points

• During childbirth, oxytocin increases uterine contractions, which stimulate further oxytocin release.

• Before eating, the body produces insulin in anticipation of an increase in blood glucose.

💡 Memory Hook

Negative feedback slows a process; positive feedback amplifies it.

📖 2. Kidney Function and Urine Formation

🔑 Key Concepts & Definitions

• Nephron: A filtering unit in the cortex and medulla of each kidney that filters blood to form urine.

★ Must-know

• The kidneys regulate water balance, blood pH, and blood concentrations of sodium, phosphorus, carbon, and calcium.

• Urine formation involves glomerular filtration, tubular reabsorption, tubular secretion, and further water reabsorption into the blood.

Further detail

• The kidneys secrete erythropoietin, which stimulates red blood cell production, and activate vitamin D production.

• Urine contains these wastes and ions:

  • urea
  • uric acid
  • creatinine
  • potassium ions
  • chloride ions

💡 Memory Hook

Filter, reclaim, secrete, reclaim water.

📖 3. Kidney Regulation of Homeostasis

🔑 Key Concepts & Definitions

• Water-sodium homeostasis: The maintenance of balance between water and sodium in the body.

★ Must-know

• Antidiuretic hormone (ADH) causes the kidneys to reabsorb more water, reducing water loss in urine.

• Aldosterone causes the kidneys to reabsorb sodium and eliminate potassium.

• When blood pressure is too low, renin initiates a response that retains sodium and water, thereby increasing blood pressure.

• The kidneys help maintain blood pH around 7.4 by eliminating hydrogen ions in urine and acting as a buffer against large pH changes.

Further detail

• The lungs help control blood carbon dioxide levels by changing respiration.

💡 Memory Hook

Low pressure triggers renin → sodium and water retention → increased pressure.

📖 4. Reproductive Hormones and Aging

★ Must-know

• At puberty, the hypothalamus releases GnRH, which stimulates the anterior pituitary to release FSH and LH.

• In males, FSH stimulates the testes, while LH stimulates testosterone production; these hormones support development of the genital organs and sexual characteristics.

• In male reproductive hormone regulation, FSH stimulates inhibin secretion by the testes, and inhibin negatively feeds back on the pituitary to reduce FSH.

• In females, FSH and LH stimulate the ovaries to produce estrogens, which support development of sexual characteristics, and progesterone, which regulates the menstrual cycle.

Further detail

• In males, testosterone released by the testes exerts negative feedback on the hypothalamus when it is overproduced.

📌 Andropause is an age-related decrease in testosterone, whereas menopause involves decreased blood levels of estrogen and progesterone.

💡 Memory Hook

Inhibin reduces FSH; LH drives testosterone release.

📖 5. Neurons and Nerve Impulses

🔑 Key Concepts & Definitions

• Neuron: A cell that transmits information in the form of nerve impulses.
• Action potential: An electrical impulse that propagates along an axon and occurs only if a stimulus reaches the threshold.

★ Must-know

• Dendrites receive information, the cell body processes it, and the axon transmits it to the next neuron through synapses.

• Schwann cells form myelin around the axon, allowing the impulse to travel faster from one node of Ranvier to the next.

• The three neuron types carry messages as follows:

  • Sensory neurons carry messages from sensory organs toward the central nervous system.
  • Motor neurons carry messages from the central nervous system to muscles or glands.
  • Interneurons transmit between sensory and motor neurons.

Further detail

• Nerve impulse transmission involves reception and conduction, interpretation, organization, and transmission of a response.

💡 Memory Hook

Dendrites receive, the cell body processes, and the axon transmits.

📖 6. Synapses and Neurotransmitters

🔑 Key Concepts & Definitions

• Voltage-gated channel: A channel that opens in response to an electrical current.
• Saltatory conduction: The propagation of an action potential by jumping from one node of Ranvier to the next along a myelinated axon.

📝 Essential Points

• At rest, a neuron does not transmit an impulse, and its membrane is polarized, with the outside more positive than the inside.

• An action potential proceeds through depolarization, repolarization, hyperpolarization, and return to resting conditions.

• An action potential propagates when depolarization in one region opens sodium channels in the adjacent region, while hyperpolarization helps ensure one-way propagation.

📌 An electrical synapse passes an action potential directly between cell membranes through intercellular channels that allow ions to flow, whereas a chemical synapse passes a message using neurotransmitters.

💡 Memory Hook

At a chemical synapse: signal, calcium, release, receptor, breakdown.

📖 7. Drugs and Neural Signaling

★ Must-know

• At a chemical synapse, an arriving electrical signal triggers calcium entry and neurotransmitter release, receptor binding, ion-channel opening, and neurotransmitter breakdown.

📌 An excitatory postsynaptic potential increases the chance of an action potential, whereas an inhibitory postsynaptic potential decreases that chance.

Further detail

• Acetylcholine is associated with these functions:

  • muscle contraction
  • wakefulness
  • attention
  • thirst
  • anger

• Dopamine is associated with these functions:

  • movement
  • posture
  • mood
  • dependence
  • reward

• GABA is associated with these functions:

  • motor control
  • vision
  • anxiety

• Glutamate is excitatory and is associated with learning and memory; an imbalance of glutamate is associated with memory problems in Alzheimer's disease.

• Noradrenaline is excitatory depending on the receptor and is associated with attention, emotions, sleep, dreams, and learning; dysregulation is associated with mood disorders similar to bipolar disorder.

• Serotonin is excitatory depending on the receptor and is associated with temperature regulation, sleep, mood, appetite, and pain; imbalance is associated with depression, suicide, impulsive behavior, and aggression.

💡 Memory Hook

Agonists activate like a neurotransmitter; antagonists block its receptor.

📖 8. Brain Regions and Functions

★ Must-know

📌 An agonist produces an effect like a neurotransmitter, whereas an antagonist blocks the neurotransmitter's receptor.

📌 A reuptake inhibitor prevents neurotransmitter reuptake so it remains in the synapse, whereas a secretion inhibitor prevents neurotransmitter release.

Further detail

• Botulinum toxin inhibits acetylcholine release, preventing muscle contraction and causing paralysis; it is used especially for wrinkles.

• Nicotine acts as an agonist by imitating acetylcholine at nicotinic receptors, is addictive, and produces pleasure associated with dopamine release.

• Cobratoxin antagonizes acetylcholine receptors at muscles, preventing muscle signaling and causing paralysis.

• Fluoxetine (Prozac) inhibits serotonin reuptake, leaving serotonin in the synapse for longer.

📖 9. Spinal Cord and Reflexes

📝 Essential Points

• Caffeine antagonizes adenosine receptors; adenosine promotes fatigue, while caffeine is associated with motivation, pleasure, and increased wakefulness.

• Alcohol affects decision-making, memory, and impulse control, and it binds to GABA receptors so their channels open more easily or for longer, allowing more chloride ions into the neuron.

• The course associates these drugs with the following effects:

  • Heroin: pain relief.
  • Marijuana: relaxation, calm, and a high.
  • Methamphetamine: pleasure, well-being, and deep joy.
  • Cocaine: inability to stay still.

💡 Memory Hook

Stimulus → receptor → sensory neuron → interneuron → motor neuron → muscle.

📖 10. Peripheral Nervous System Divisions

★ Must-know

• The cerebellum coordinates muscle contraction, automatic movements such as walking and balance, and voluntary movements such as writing or hitting a tennis ball.

• The pons connects the right and left parts of the brain, while the medulla carries messages between the brain and spinal cord and controls reflexes and automatic homeostatic functions.

• The midbrain processes sensory impulses, especially visual and auditory information, while the forebrain is involved in thought, learning, and emotions and includes the thalamus, hypothalamus, and telencephalon.

• The hypothalamus regulates these functions:

  • temperature
  • blood pressure
  • water level
  • hunger
  • thirst
  • emotional responses

Further detail

• The medulla controls these functions:

  • heartbeat
  • blood-vessel constriction and dilation
  • breathing
  • swallowing
  • coughing

• The thalamus relays sensory information to the brain and is associated with consciousness, wakefulness, and pain tolerance.

• The pituitary regulates several glands in the body and works with the hypothalamus.

💡 Memory Hook

Sympathetic prepares for stress; parasympathetic supports rest and relaxation.