Chapter 3 Biological Bases of Behavior

Chapter 3: Biological Bases of Behavior

Overview

• Neuroanatomy/neurophysiology

• Nervous System/Brain/Endocrine System

• Genetics/Genetic Disorders

• Warm up with Crash Course's Introduction

Big Idea: Neurons & Behavior

• Neuroanatomy: study of neuron structure

• Neurophysiology: study of neuron function

• Neurons: individual nerve cells composing the nervous system

• Each neuron has distinct parts, essential for brain structure.

Components of Neurons

Neuron Structure and Functions

• Primary Motor Cortex: responsible for voluntary movements.

• Corticospinal Tract: pathway for upper motor neuron signals.

• Spinal Cord: conveys impulses between the brain and body.

• Interneurons: process information between sensory and motor neurons.

• Lower Motor Neuron: directly innervates skeletal muscle.

Neuronal Communication

• Axonal Hilock: integrates incoming signals and initiates action potentials.

• Axon: transmits the action potential away from the cell body.

• Myelin: insulates axons, speeding up signal transmission.

• Presynaptic Neuron: sends signals.

• Dendrites: receive signals from other neurons.

Neuroanatomy Details

Key Parts of a Neuron

• Nucleus: contains genetic material.

• Cell Body (Soma): metabolic center of the neuron.

• Telodendria: branches leading to synaptic terminals.

• Axon Hillock: triggers action potentials.

• Synaptic Terminals: release neurotransmitters into the synapse.

• Endoplasmic Reticulum: synthesizes proteins.

• Mitochondrion: provides energy.

• Golgi Apparatus: packages and distributes proteins.

Dendrites and Axons

• Dendrites: Receive signals, grow to form synapses.

• Axons: Long, wire-like, terminates in terminal buttons.

Myelin Sheath

• Facilitates faster signal transmission.

• Not all neurons have myelin sheaths.

• Nodes of Ranvier: gaps in myelin sheath for action potentials.

Neurophysiology: Function of Neurons

Action Potentials

• Neurons maintain a resting potential of -70mV.

• Neurotransmitters bind to receptor sites on dendrites.

• If threshold is met, positive ions enter, causing the neuron to fire.

• All-or-Nothing Principle: Neurons either fire fully or not at all.

The Synapse

1. Action potential arrives at the axon terminal.

2. Vesicles fuse with the membrane, releasing neurotransmitters.

3. Neurotransmitters cross the synaptic cleft.

4. Bind to receptors on the postsynaptic neuron.

Neurotransmitters

• Excitatory: Promote action in the receiving neuron (e.g., Glutamate).

• Inhibitory: Deter action in the receiving neuron (e.g., GABA).

Important Neurotransmitters and Their Functions

Nervous System Overview

Central Nervous System (CNS)

• Composed of brain and spinal cord.

• Receives sensory information, initiates responses, controls memories, thoughts, and emotions.

• Controls reflex activities.

Peripheral Nervous System (PNS)

• Consists of all nerves outside CNS.

• Divided into somatic (voluntary) and autonomic (involuntary) nervous systems.

Autonomic Nervous System

• Controls involuntary bodily functions.

Divisions

• Sympathetic Division: