The Biological Mind Chapter 4

Biological Psychology Biological Psychology : a rich, interdisciplinary field of study that combines the methods and theories of psychology with those of biology, physiology, biochemistry, the neurosciences, and related fields –Studies the relationship between behavior and bodily processes and systems Neuroscience : the study of the nervous system, especially the brain

The Nervous System Central Nervous System (CNS): the brain and spinal cord Peripheral Nervous System (PNS): the nerves exiting the central nervous system that carry sensory and motor information to and from the rest of the body

The Structures of the Brainstem The hindbrain is composed of the: – Medulla: life-sustaining functions – Pons: sleep, arousal, and facial expression – Cerebellum: motor coordination The midbrain is involved in sensory reflexes, movement, and pain; connects hindbrain to upper brain areas. Together, the hindbrain and midbrain make up the brainstem. Reticular Formation : runs the length of the brainstem’s core; participates in the control of mood, arousal, and sleep

Subcortical Structures and Their Functions Major Structures: – Thalamus: sensory relay center – Hypothalamus: involved with motivation and homeostasis – Amygdala: plays a role in identifying, remembering, and responding to fear and aggression – Hippocampus: essential to the formation, storage, and retrieval of long- term memories Other Structures: –Basal Ganglia: involved in voluntary movement –Cingulate Cortex: important in decision making, emotion, empathy, memory, vision Amygdala Basal GangliaThalamus Amygdala Hypothalamus Hippocampus Cingulate Cortex

The Cerebral Hemispheres and the Corpus Callosum The corpus callosum is a large bundles of axons that connects the two cerebral hemispheres. The cerebral cortex is the thin layer of cells covering the outer surface of the hemispheres. The cerebrum, hypothalamus, and thalamus are collectively referred to as the forebrain.

Lobes of the Cerebral Cortex Frontal Lobe: executive function; motor cortex; Broca’s Area Temporal Lobe: primary auditory cortex; complex visual stimuli; Wernicke’s Area Parietal Lobe: somatosensory cortex; sensory processing Occipital Lobe: primary visual cortex

The Body’s Representation in the Brain Homunculus: ‘little man’ –More area on the cortex is assigned to body parts that move the most (motor cortex) and that are the most sensitive (somatosensory cortex).

Studying the Brain TechnologyProcedureWhat Questions Can We Answer? electroencephalogram (EEG) electrodes (to track electrical activity) What is a person’s state of arousal? positron emission tomography (PET) radioactively tagged glucose or oxygen (to track chemical activity) What parts of the brain are active during a particular task? functional magnetic resonance imaging (fMRI) magnets (to track the flow of oxygen) What parts of the brain are active during a particular task?

The Spinal Chord Together, with the brain, makes up the central nervous system Motor neurons, sensory neurons, and interneurons Protections: –Encased entirely in bone –Suspended in cerebrospinal fluid Spinal Reflexes : simple, automatic behaviors that are processed in the spinal chord

The Peripheral Nervous System Peripheral Nervous System (PNS): includes all of the nerves lying outside the CNS – Somatic Division – Autonomic division sympathetic division parasympathetic division

The Somatic Nervous System and the Cranial Nerves Somatic Nervous System: –transmits commands for voluntary movement from the central nervous system to the muscles –brings sensory input back to the CNS for further processing

The Autonomic Nervous System The autonomic nervous system is responsible for: – homeostasis : the regulation of important body functions such as temperature and thirst Parasympathetic Division –our fight-or-flight response to emergencies Sympathetic division

Neurons process and transmit information – Dendrites : portions of neurons that receive signals – Axon : portions of neurons that send signals Glial Cells: support cells that assist neurons The Structure and Function of Neurons Glia Blood Vessel Neuron Myelin

Axons Transmit Information Axon : portions of neurons that send signals Axon Terminals : contain synaptic vesicles which store and release neurotransmitters

Dendrites Receive Information Dendrites : portions of neurons that receive signals Neurotransmitters communicate with receptors on the dendrites.

Electrical signaling: action potential Chemical signaling: neurotransmitters Neural Communication: A Two-Step Process

Electrical Signaling: Generating an Action Potential Resting Potential: electrical charge when the neuron is not being stimulated or inhibited Action Potential : a brief, electrical impulse by which information is transmitted along the axon of a neuron –all-or-none –regenerative Absolute Refractory Period: time during which another action potential is impossible

Electrical Signaling: Propagating an Action Potential Propagation: the duplication of the electrical signal down the length of the axon to the axon terminal –myelinated axons Nodes of Ranvier –unmyelinated axons Once the action potential reaches the axon terminal, the neural communication system switches from an electrical signaling system to a chemical signaling one.

Chemical Signaling: Releasing Neurotransmitters When an action potential arrives at the axon terminal, neurotransmitters are released. –Neurotransmitters are stored in tiny sacs called synaptic vesicles. When a nerve impulse reaches the end of an axon, vesicles move to the surface and release neurotransmitters into the synapse.

Presynaptic Neuron Postsynaptic Neuron Chemical Signaling Synapse

Chemical Signaling: Synaptic Transmission

1 Synthesis and storage of neurotransmitter molecules in synaptic vesicles 2 Release of neurotransmitter molecules into synaptic cleft 5 Reuptake of neurotransmitters sponged up by the presynaptic neuron 4 Inactivation (by enzymes) or removal (drifting away) of neurotransmitters 3 Binding of neurotransmitters at receptor sites on postsynaptic membrane Chemical Signaling: Synaptic Transmission

Important Neurotransmitters and Their Effects Acetylcholine Dopamine Serotonin Norepinephrine GABA – gamma- aminobutyric acid Endorphins

The Endocrine System Endocrine system : a system of glands that controls secretion of blood- borne chemical messengers Hormones : blood-borne chemical messengers that influence target tissues and glands