Biological Bases of Behavior and The Nervous System: Psychology Study Notes

Biological Bases of Behavior and Consciousness

Major Parts of a Neuron and Their Functions

Neurons are specialized cells that transmit information throughout the nervous system. Understanding their structure is essential for grasping how neural communication occurs.

• Cell Body (Soma): Contains the nucleus and integrates messages received from axons, conducting them toward the cell body.

• Dendrites: Neuron extensions that receive and integrate messages from axons, and conduct them toward the cell body.

• Axon: The long extension of some neurons that helps speed neural impulses.

• Terminal Branches of Axon: Form junctions with other cells.

Synapse: The junction between an axon tip of a sending neuron and the dendrite or cell body of a receiving neuron.

Synaptic Gap: The tiny gap at the synapse.

Action Potentials

An action potential is a brief impulse or electrical signal that travels down an axon. It is the means by which neurons communicate.

• Definition: Nerve impulse or electrical signal that travels down an axon.

• Process: The action potential is triggered when a neuron receives enough excitatory signals to reach a threshold, causing a rapid change in membrane potential.

• All-or-None Response: Neurons either fire at full strength or not at all. The intensity of the stimulus does not affect the strength of the action potential, only its frequency.

Example: When you touch a hot surface, sensory neurons fire action potentials to signal pain to your brain.

Neural Communication

Neurons communicate with each other through synapses, where neurotransmitters are released and bind to receptors on the postsynaptic neuron.

• Presynaptic Neuron: The neuron sending the signal.

• Postsynaptic Neuron: The neuron receiving the signal and integrating it.

• Neurotransmitters: Chemical messengers that cross the synaptic gap to carry messages to other neurons.

• Excitatory vs. Inhibitory Signals: Excitatory neurotransmitters increase the likelihood of the postsynaptic neuron firing, while inhibitory neurotransmitters decrease it.

Threshold: The minimum stimulus needed to trigger an action potential.

Refractory Period: Brief resting pause after a neuron fires, during which it cannot fire again.

Neurotransmitters and Their Functions

Neurotransmitters play a crucial role in regulating mood, movement, and cognition. Imbalances can lead to various psychological disorders.

• Dopamine: Influences movement, learning, attention, and emotion. Excess dopamine is linked to schizophrenia; deficiency is linked to Parkinson's disease.

• Serotonin: Affects mood, hunger, sleep, and arousal. Undersupply is linked to depression.

• Endorphins: Influence the perception of pain or pleasure. Drugs that suppress endorphin supply can reduce pain but also lower natural endorphin levels.

The Nervous System

Purpose and Structure

The nervous system is the body's speedy, electrochemical communication network, consisting of all the nerve cells of the central and peripheral nervous systems.

• Nerves: Electrical cables formed from axon bundles.

• Central Nervous System (CNS): Brain and spinal cord; processes information and coordinates activity.

• Peripheral Nervous System (PNS): Connects the CNS to organs and parts of the body; contains all nerves outside the CNS.

Types of Neurons

• Motor (Efferent) Neuron: Carries information away from the CNS to operate muscles and glands.

• Sensory (Afferent) Neuron: Carries information toward the CNS from the sensory organs.

• Interneuron: Sends information between sensory and motor neurons.

Nervous System Divisions

Division	Main Function
Central Nervous System (CNS)	Processes information; consists of brain and spinal cord
Peripheral Nervous System (PNS)	Connects CNS to organs and limbs; subdivided into Somatic and Autonomic systems
Somatic Nervous System	Controls voluntary movements of skeletal muscles
Autonomic Nervous System	Controls involuntary functions (heartbeat, digestion); subdivided into Sympathetic and Parasympathetic systems
Sympathetic Nervous System	Activates "fight or flight" response
Parasympathetic Nervous System	Calms the body after stress; "rest and digest"

Key Points on Nervous System Divisions

• Somatic Nervous System: Controls voluntary muscle movement and conscious actions.

• Autonomic Nervous System: Regulates involuntary functions such as heartbeat and digestion.

• Sympathetic Nervous System: Prepares the body for stressful situations (fight or flight).

• Parasympathetic Nervous System: Restores the body to a calm state after stress.

Example: When you are startled, your sympathetic nervous system increases your heart rate and dilates your pupils. After the threat passes, the parasympathetic system calms you down.

The Endocrine System

Structure and Function

The endocrine system is composed of glands that produce and secrete hormones, which regulate bodily functions by traveling through the bloodstream.

• Hormones: Chemical messengers secreted by glands; regulate metabolism, growth, mood, and more.

• Pituitary Gland: The "master gland" that regulates other glands and controls growth.

• Adrenal Glands: Release hormones involved in stress response (e.g., adrenaline).

Hormones vs. Neurotransmitters

• Hormones: Travel through the bloodstream; slower, longer-lasting effects.

• Neurotransmitters: Travel across synapses; faster, shorter-lasting effects.

Major Endocrine Glands and Their Functions

Gland	Main Function
Pituitary	Regulates growth and controls other glands
Adrenal	Releases hormones for stress response
Thyroid	Regulates metabolism

Brain Structures and Their Functions

Major Brain Regions

• Cerebellum: Located at the rear of the brainstem; aids in judgment of time, discrimination of sound and texture, and emotional control. Coordinates voluntary movement and balance.

• Medulla: Base of the brainstem; controls heartbeat and breathing.

• Thalamus: Top of the brainstem; relays information from sensory organs to the cerebral cortex.

• Corpus Callosum: Large band of neural fibers connecting the left and right hemispheres; transmits information between hemispheres.

Limbic System Functions

• Amygdala: Involved in emotion, especially fear and aggression.

• Hippocampus: Involved in memory formation.

• Hypothalamus: Regulates hunger, thirst, sexual drive, and body temperature; controls the pituitary gland.

Summary Table: Brain Structures

Structure	Function
Cerebellum	Coordinates movement and balance
Medulla	Controls heartbeat and breathing
Thalamus	Relays sensory information
Corpus Callosum	Connects left and right hemispheres
Amygdala	Emotion (fear, aggression)
Hippocampus	Memory formation
Hypothalamus	Regulates drives and pituitary gland

Key Equations and Concepts

• Action Potential: $\text{Action Potential} = \text{Rapid change in membrane potential}$

• All-or-None Law: $\text{Neuron fires at full strength or not at all}$

Additional info:

• Some content was expanded for clarity and completeness, including definitions and examples.

• Tables were recreated to summarize divisions and functions of the nervous and endocrine systems.