Human Physiology Exam 1

Physiology

Study of biological function and how body systems work

Pathophysiology

Study of how disease or injury disrupts normal physiology

Homeostasis

Maintenance of a stable internal environment

Negative feedback

Response counteracts the original change

Positive feedback

Response amplifies the original change

Integrating center

Structure that processes information and initiates a response

Intrinsic regulation

Local control within an organ (autoregulation)

Extrinsic regulation

Control of organs by nervous or endocrine systems

Simple diffusion

Passive movement of lipid-soluble molecules down a concentration gradient

Facilitated diffusion

Passive transport using carrier proteins

Active transport

Movement against a gradient using ATP

Osmosis

Diffusion of water across a selectively permeable membrane

Aquaporins

Water channels that facilitate osmosis

Tonicity

Ability of a solution to change cell volume

Isotonic solution

No net change in cell volume

Hypertonic solution

Cell shrinks due to water loss

Hypotonic solution

Cell swells due to water gain

Na⁺/K⁺ pump

Moves 3 Na⁺ out and 2 K⁺ into the cell using ATP

Ca²⁺ pump

Removes Ca²⁺ from cytoplasm to maintain low intracellular calcium

Neuron

Excitable cell that conducts electrical signals

Dendrites

Receive incoming signals

Axon

Conducts action potentials away from the cell body

Axon hillock

Site where action potentials are initiated

Synapse

Functional connection between neurons

Sensory neuron

Conducts impulses toward the CNS

Motor neuron

Conducts impulses away from the CNS

Interneuron

Integrates signals within the CNS

Nerve

Bundle of axons in the PNS

Tract

Bundle of axons in the CNS

Oligodendrocytes

Myelinate axons in the CNS

Schwann cells

Myelinate axons in the PNS

Neurotrophins

Proteins that support neuron survival and growth

Nogo protein

Inhibits axon regeneration in the CNS

Resting membrane potential

−70 mV due to ion gradients

Excitability

Ability of neurons to change membrane potential

Graded potential

Local, variable-strength membrane potential change

EPSP

Depolarizing graded potential

IPSP

Hyperpolarizing graded potential

Threshold

−55 mV required to trigger an action potential

Action potential

Rapid, all-or-none depolarization of the membrane

All-or-none law

Action potentials occur fully or not at all

Depolarization

Na⁺ influx makes membrane more positive

Repolarization

K⁺ efflux restores negative membrane potential

After-hyperpolarization

Membrane becomes more negative than resting

Absolute refractory period

No new action potential possible

Relative refractory period

Strong stimulus required to trigger action potential

Cable properties

Ability of neurons to conduct charge passively

Saltatory conduction

Action potentials jump between nodes of Ranvier

Nodes of Ranvier

Gaps in myelin with high Na⁺ channel density

Myelinated axon

Faster conduction speed

Unmyelinated axon

Slower conduction speed

Axon diameter

Larger diameter increases conduction speed

Chemical synapse

Uses neurotransmitters to signal

Electrical synapse

Uses gap junctions for direct ion flow

Synaptic cleft

Space between presynaptic and postsynaptic cells

Neurotransmitter

Chemical messenger released at synapse

Synaptic vesicles

Store neurotransmitters

SNARE proteins

Dock and fuse vesicles to membrane

Synaptotagmin

Calcium sensor triggering neurotransmitter release

Voltage-gated Ca²⁺ channels

Allow Ca²⁺ entry into presynaptic terminal

Ionotropic receptor

Ligand-gated ion channel

Metabotropic receptor

G-protein-coupled receptor using second messengers

Dopamine

Neurotransmitter involved in movement, reward, cognition

Nigrostriatal pathway

Dopamine pathway controlling movement

Mesolimbic pathway

Dopamine pathway involved in reward and addiction

Glutamate

Major excitatory neurotransmitter

AMPA receptor

Fast glutamate receptor allowing Na⁺ influx

NMDA receptor

Glutamate receptor requiring depolarization and ligand

Long-term potentiation (LTP)

Strengthening of synapses during learning

GABA

Main inhibitory neurotransmitter

GABA_A receptor

Ionotropic Cl⁻ channel receptor

Benzodiazepines

Enhance GABA_A receptor activity

Acetylcholine (ACh)

Neurotransmitter used by motor neurons

Nicotinic receptor

Ionotropic ACh receptor

Muscarinic receptor

Metabotropic ACh receptor

Neuromuscular junction

Synapse between motor neuron and muscle

End-plate potential

EPSP at the neuromuscular junction

Myasthenia gravis

Autoimmune blockade of nicotinic ACh receptors

Acetylcholinesterase (AChE)

Enzyme that breaks down ACh

Cerebrum

Largest brain region responsible for higher functions

Thalamus

Sensory relay and integration center

Hypothalamus

Regulates autonomic and endocrine systems

Pineal gland

Secretes melatonin

Melatonin

Hormone regulating circadian rhythms

Pons

Controls respiration rate and cranial nerves

Medulla oblongata

Controls vital functions like breathing and heart rate

Cerebellum

Coordinates movement and motor learning

Broca’s area

Speech production

Wernicke’s area

Speech comprehension

Conduction aphasia

Damage to arcuate fasciculus

Arcuate fasciculus

Connects Broca’s and Wernicke’s areas

Hippocampus

Formation of episodic memories

Amygdala

Emotional processing and fear memory

Guillian-Barre Syndrome

The T cells of the immune system attack the myelin sheath of the PNS. This produces rapid onset symptoms that include muscle weakness

Multiple Sclerosis

Produced by an autoimmune attack by T lymphocytes causing lymphocytes and monocytederived macrophages to enter the brain and target the myelin sheaths of the CNS causing demyelination

Huntington’s Disease

Low GABA, leading to nerve cells firing too often and easily

Huntington’s Disease

Degeneration of GABA-secreting neurons in the cerebellum