Autonomic Nervous System Overview

Autonomic Nervous System (ANS)

The part of the peripheral nervous system that controls involuntary functions by regulating glands, smooth muscles, and heart.

Sympathetic Nervous System

The division of the autonomic nervous system that prepares the body for 'fight or flight' responses during stressful situations.

Parasympathetic Nervous System

The division of the autonomic nervous system that conserves energy and restores the body to a state of calm (often referred to as 'feed and breed').

Dual Innervation

The phenomenon where most organs receive nerve fibers from both the sympathetic and parasympathetic divisions of the autonomic nervous system.

Cholinergic Fibers

Nerve fibers that release acetylcholine (ACh) as their neurotransmitter.

Adrenergic Fibers

Nerve fibers that release norepinephrine (NE) as their neurotransmitter.

Autonomic Tone

The continuous, passive partial state of contraction of the muscles, providing an internal tension that helps maintain posture.

Visceral Reflexes

Reflexes mediated by the autonomic nervous system that control organ function such as heart rate, blood pressure, and digestion.

Epinephrine (Adrenaline)

A hormone released by the adrenal medulla that enhances the fight-or-flight response.

Muscarinic Receptors

Cholinergic receptors located on the target organs of the parasympathetic nervous system.

Nicotinic Receptors

Cholinergic receptors located on the ganglia of both the sympathetic and parasympathetic nervous systems.

Alpha-adrenergic Receptors

Adrenergic receptors that typically mediate vasoconstriction.

Beta-adrenergic Receptors

Adrenergic receptors involved in mediating effects like increased heart rate and bronchodilation.

Sympathomimetic Drugs

Drugs that mimic the effects of the sympathetic nervous system.

Parasympatholytic Drugs

Drugs that inhibit the actions of the parasympathetic nervous system.

Vagal Tone

The activity of the vagus nerve; part of the parasympathetic system which promotes 'rest and digest' functions.

Neurotransmitter

Chemicals that transmit signals across a synapse from one neuron to another or to a target effector.

Bradycardia

An abnormally slow heart rate, often a result of increased parasympathetic activity.

Endocrine Response

Hormonal response regulated by the autonomic nervous system, such as the secretion of epinephrine.

Acetylcholine (ACh)

The primary neurotransmitter used by cholinergic fibers.

Neurons

The basic building blocks of the nervous system that transmit information through electrical and chemical signals.

Dendrites

Branch-like structures of neurons that receive messages from other neurons.

Axon

A long, thin part of a neuron that transmits electrical impulses away from the cell body.

Synapse

The junction between two neurons where neurotransmitters are released to transmit signals.

Myelin Sheath

A protective covering that surrounds axons, helping to speed up nerve impulse conduction.

Action Potential

An electrical impulse that travels down the axon when a neuron is activated.

Resting Potential

The electrical charge difference across the membrane of a resting neuron.

Neuroplasticity

The ability of the brain to change and adapt in response to experience and learning.

Central Nervous System (CNS)

The part of the nervous system that includes the brain and spinal cord.

Peripheral Nervous System (PNS)

The part of the nervous system that connects the CNS to the rest of the body, including limbs and organs.

Reflex Arc

A simple neural pathway that mediates a reflex action, involving sensory and motor neurons.

Glial Cells

Supportive cells in the nervous system that assist, nourish, and protect neurons.

Neurotransmitter Release

The process whereby neurotransmitters are released from the presynaptic neuron into the synapse.

Inhibitory Neurotransmitters

Neurotransmitters that decrease the likelihood of a neuron firing an action potential.

Excitatory Neurotransmitters

Neurotransmitters that increase the likelihood of a neuron firing an action potential.

Serotonin

A neurotransmitter that contributes to feelings of well-being and happiness.

Dopamine

A neurotransmitter involved in reward, motivation, and pleasure; often linked to motor control.

Acetylcholine

A neurotransmitter associated with muscle activation and memory function.

Norepinephrine

A neurotransmitter that plays a role in attention, emotions, and responding actions.

Endorphins

Neurotransmitters that function as natural painkillers and stress relievers.

Blood-Brain Barrier

A selective barrier that prevents certain substances from entering the brain from the bloodstream.

Brainstem

The part of the brain that controls vital life functions, such as breathing and heartbeat.

Cerebellum

A region of the brain that plays an important role in motor control and coordination.

Cerebral Cortex

The outer layer of the brain involved in complex cognitive functions, such as perception and reasoning.

Corpus Callosum

A bundle of nerve fibers that connects the left and right hemispheres of the brain.

Hippocampus

A brain region important for memory formation and spatial navigation.

Amygdala

A brain structure involved in emotional regulation and processing.

Thalamus

A brain structure that acts as a relay station for sensory and motor signals.

Hypothalamus

A brain region that regulates homeostasis and influences the autonomic nervous system.

Frontal Lobe

The area of the brain associated with reasoning, planning, problem-solving, and emotional control.

Parietal Lobe

The area of the brain that processes sensory information, such as touch and taste.

Occipital Lobe

The area of the brain responsible for vision and visual processing.

Temporal Lobe

The area of the brain involved in auditory processing and memory.