Biopsychology A1

Nervous System Divisions

The nervous system is divided into the central nervous system (CNS: brain and spinal cord) and the peripheral nervous system (PNS: all nerves outside the CNS).

Central Nervous System (CNS)

Comprised of brain and spinal cord; responsible for processing information, controlling behaviour, and coordinating responses.

Peripheral Nervous System (PNS)

Splits into the somatic nervous system (voluntary movement) and autonomic nervous system (involuntary processes).

Somatic Nervous System

Controls voluntary muscle movement and carries sensory information to the CNS.

Autonomic Nervous System

Regulates involuntary functions such as heart rate, breathing, digestion; splits into sympathetic and parasympathetic branches.

Sympathetic Nervous System

Activates 'fight or flight' response; increases heart rate, dilates pupils, inhibits digestion.

Parasympathetic Nervous System

Restores body to resting state ('rest and digest'); slows heart rate, increases digestion.

Neuron Structure

Neurons consist of dendrites (receive signals), cell body/soma (contains nucleus), axon (carries impulse), myelin sheath (insulates), nodes of Ranvier (speed conduction), and axon terminals.

Function of Neurons

Transmit electrical and chemical signals throughout the nervous system to communicate information.

Sensory Neurons

Carry information from sensory receptors to the CNS; long dendrites, short axons.

Relay Neurons

Connect sensory and motor neurons within the CNS; short dendrites, short axons.

Motor Neurons

Send signals from CNS to muscles or glands; short dendrites, long axons.

Action Potential

Electrical impulse generated when a neuron fires, caused by rapid change in electrical charge across the membrane.

Synaptic Transmission

Process by which neurons communicate: electrical impulse triggers neurotransmitter release, which crosses synaptic gap and binds to receptors.

Neurotransmitters

Chemical messengers that transmit signals across the synapse from one neuron to another.

Excitatory Neurotransmitters

Increase likelihood that the postsynaptic neuron will fire (e.g., glutamate).

Inhibitory Neurotransmitters

Decrease likelihood of postsynaptic firing (e.g., GABA); calm the nervous system and regulate anxiety.

Dopamine

Can be excitatory or inhibitory; involved in reward, movement, and motivation.

Serotonin

Generally inhibitory; involved in mood regulation, sleep, and appetite.

Acetylcholine

Excitatory; involved in muscle contraction and memory.

Synaptic Reuptake

Neurotransmitters left in the synaptic cleft are reabsorbed into the presynaptic neuron to be reused.

Endocrine System Function

Network of glands that secrete hormones into the bloodstream to regulate processes such as growth, metabolism, and stress responses.

Hormones

Chemical messengers produced by endocrine glands; act more slowly than neurotransmitters but have widespread effects.

Pituitary Gland

The 'master gland' controlling release of hormones from all other endocrine glands.

Adrenal Glands

Located above kidneys; release adrenaline, noradrenaline, and cortisol during stress.

HPA Axis

Hypothalamus → Pituitary gland → Adrenal cortex; responsible for prolonged stress response through cortisol release.

Fight or Flight Response

Physiological response to stress involving activation of the sympathetic nervous system and release of adrenaline.

Role of Adrenaline

Increases heart rate, breathing rate, blood flow to muscles, and energy availability to prepare for action.

Acute Stress Response (SAM System)

Sympathetic nervous system activates adrenal medulla to release adrenaline and noradrenaline.

Rest and Digest Response

After threat passes, parasympathetic nervous system returns body to baseline by lowering heart rate and resuming digestion.

Cortisol in Stress

Released by adrenal cortex during long-term stress; provides energy but suppresses immune system.

Weakness of Fight-or-Flight

Model is oversimplified and may not apply equally to females ('tend and befriend' alternative).