Module 4
Neural and Hormonal Systems
Neural Communication
The Nervous System
Neural and Hormonal Systems
The Endocrine System
History of the Mind
Plato correctly located mind in the brain, however his student Aristotle believed that mind was in the heart.
In 1800, Franz Gall suggested, that bumps of the skull represented mental abilities. His theory though incorrect, nevertheless proposed different mental abilities were modular.
Neural Communication
The body’s information system is built from billions of interconnected cells called neurons.
We are biopsychosocial systems.
Neural Communication
Neurobiologists and other investigators understand that information processing in humans and animals operate similarly.
Neuron
A nerve cell or a neuron consists of many different parts.
Parts of a Neuron
Cell Body: Life support center of the neuron.
Dendrites: Branching extensions at the cell body. Receives messages from other neurons.
Axon: Long single extension of a neuron, covered with myelin [MY-uh-lin] sheath to insulate and speed up messages through neurons.
Terminal Branches of axon: Branched ending of axons. Transmitting messages to other neurons.
Action Potential
A neural impulse. A brief electrical charge that travels down an axon generated by the movement of positively charged atoms in and out of channels in the axon’s membrane.
Depolarization & Hyperpolarization
Depolarization: Depolarization occurs, when positive ions enter the neuron, making it more susceptible to fire an action potential. When negative ions enter the neuron making it less susceptible to fire, hyperpolarization occurs.
Threshold
Threshold: Each neuron receives depolarizing and hyperpolarizing currents from many neurons. When the depolarizing current (positive ions) minus the hyperpolarizing current (negative ions) exceed minimum intensity (threshold) the neuron fires an action potential.
Refractory Period & Pumps
Refractory Period: After a neuron has fired an action potential it pauses for a short period to recharge itself to fire again.
Sodium-Potassium Pumps: Sodium-potassium pumps pump positive ions out from the inside of the neuron, making them ready for another action potential.
Action Potential Properties
All-or-None Response: When depolarizing current exceeds the threshold a neuron will fire, and below threshold it will not.
Intensity of an action potential remains the same, throughout the length of the axon.
Synapse
Synapse [SIN-aps] a junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. This tiny gap is called the synaptic gap or cleft.
Neurotransmitters
Neurotransmitters (chemicals) released from the sending neuron, travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing it to generate an action potential.
Reuptake
Neurotransmitters in the synapse are reabsorbed into the sending neurons through the process of reuptake. This process applies brakes on neurotransmitter action.
How Neurotransmitters Influence Us
Dopamine Pathways
Neurotransmitters
Lock & Key Mechanism
Neurotransmitters bind to the receptors of the receiving neuron in a key-lock mechanism.
Agonists
Antagonists
Nervous System
The Nervous System
Nervous System: Consists of all the nerve cells. It is the body’s speedy, electrochemical communication system.
Central Nervous System (CNS): the brain and spinal cord.
Peripheral Nervous System (PNS): the sensory and motor neurons that connect the central nervous system (CNS) to the rest of the body.
The Nervous System
Kinds of Neurons
Sensory Neurons carry incoming information from the sense receptors to the CNS. Motor Neurons carry outgoing information from the CNS to muscles and glands. Interneurons connect the two neurons.
Kinds of Glia Cells
Astrocytes provide nutrition to neurons. Oligodendrocytes and Schwann cells insulate neurons as myelin.
Peripheral Nervous System
Somatic Nervous System: The division of the peripheral nervous system that controls the body’s skeletal muscles.
Autonomic Nervous System: Part of the PNS that controls the glands and other muscles.
The Nerves
Nerves consist of neural “cables” containing many axons. They are part of the peripheral nervous system, and connect muscles, glands, and sense organs to the central nervous system.
Autonomic Nervous System (ANS)
Sympathetic Nervous System: division of the ANS that arouses the body, mobilizing its energy in stressful situations.
Parasympathetic Nervous System: division of the ANS that calms the body, conserving its energy.
The Endocrine System
Hormones
Hormones are chemicals synthesized by the endocrine glands and secreted in the bloodstream. Hormones affect the brain many other tissues of the body.
Pituitary Gland
Thyroid & Parathyroid Glands
Adrenal Glands
Gonads