Nervous System Overview Quiz

Module BL1004: Animal Physiology

• This module covers animal physiology, specifically focusing on the nervous system.
• Professor Rob McAllen teaches the module at University College Cork, Ireland.
• Contact information for any questions or inquiries is provided.

Nervous System

• Electric signals in animals are studied.
• Relevant chapter and page number from a textbook (Campbell Biology, Chapter 48, pg 1125) is cited.
• Information is further explained in the module's content.

Integrated Physiological Mechanisms

• Barnacles on a rocky shore are included as an example.

Sponge Diversity

• Visuals of diverse sponge types are presented.

Sponge Film

• A visual presentation related to sponges is indicated.

Overview: Command and Control Center

• The nervous system controls feelings, perceptions, and movement.
• Functions include learning, remembering, thinking, and awareness.
• It also regulates internal bodily functions and behaviors.

Overview: Lines of Communication

• The nervous system has three main functions: sensory input, integration, and motor output.
• Sensors detect both external and internal stimuli.
• Sensory information travels along sensory neurons and is processed in the brain or ganglia.
• Interneurons integrate this information within the CNS (central nervous system).
• Motor output through motor neurons causes muscle or gland activity in response (PNS: Peripheral nervous system).
• Examples like the knee-jerk response are given.

Neurons

• Neurons are nerve cells carrying information through the body.
• Dendrites (tree-like extensions) receive signals from other neurons.
• Axons transmit signals from the terminal branches to other cells at synapses.
• Neuron organelles are mostly located in the cell body.
• Glia cells support and nourish neurons for proper nervous system function.

Neuron

• Every cell maintains a voltage difference (membrane potential) across its membrane.
• Communication happens via changes in the membrane potential.
• "Resting potential" describes the membrane potential of a neuron not transmitting signals.
• Ion pumps and ion channels maintain this resting potential.

Neuron - Formation of the Resting Potential

• At rest, the concentration of K+ is higher inside the neuron, while that of Na+ is greater outside.
• Sodium-potassium pumps use ATP energy to maintain these ion gradients across the membrane.
• These gradients constitute chemical potential energy.

Neuron - Formation of the Resting Potential

• Ion channels' opening changes chemical potential into electrical potential.
• Open K+ channels allow K+ to diffuse out.
• Trapped anions inside contribute to the neuron's negative internal charge.

Neuron - Formation of the Resting Potential

• In a resting neuron, K+ and Na+ currents are equal and opposite forces.
• This keeps the resting membrane potential stable.

Formation of Action Potentials

• A series of steps describe action potential formation, including depolarization, repolarization, and recovery.
• The action potential's formation is described and illustrated.

Formation of Action Potentials

• A refractory period follows an action potential.
• During this period, a neuron cannot generate another action potential as quickly.
• This prevents backflow of impulse and ensures one-way travel along the axon.
• The Na+ channels' temporary inactivation results in the refractory period.
• Repolarization takes place when the Na+K+ pump returns the membrane to its original polarized condition.

Conduction of Action Potentials

• Action potentials regenerate and travel long distances along the axon.
• The electrical current generated at one part of the axon triggers the adjacent part resulting in depolarization.
• The inactivation of Na+ channels prevents action potential backflow.
• Action potentials travel towards the synaptic terminals.

Conduction of Action Potentials

• Action potential speed increases with axon diameter.
• Myelin sheaths (insulating layers) speed up action potentials.
• Myelin is formed by oligodendrocytes in the CNS and Schwann cells in the PNS.

Conduction of Action Potentials

• Action potentials "jump" between gaps in the myelin sheath (Nodes of Ranvier).
• This "saltatory" conduction speeds up transmission.

Neurons communicate with other cells at synapses

• A synapse is a junction where neurons communicate with other cells.
• Electrical synapses pass electrical current between neurons.
• Chemical synapses use neurotransmitters to transmit signals.

There are two types of synapses

• Synaptic terminals release chemical messengers (neurotransmitters).
• Neurotransmitters transmit information from one neuron to another, a muscle cell, or a gland cell.

Chemical synapses

• The presynaptic neuron releases neurotransmitters into the synaptic cleft.
• Neurotransmitters bind to ligand-gated ion channels on the postsynaptic cell.
• This stimulates/modifies the electrical activity of the postsynaptic cell.
• Neurotransmitters detach from the receptors & are removed from the synaptic cleft in several ways.

Chemical synapses

• Direct synaptic transmission involves neurotransmitter binding to ligand-gated ion channels.
• Neurotransmitter binding opens ion channels, which generates a postsynaptic potential.
• After release, neurotransmitters can diffuse away, be taken up by surrounding cells, or be broken down by enzymes.

"Neural Regulation in Animals"

• Additional content is cited from Campbell (Chapter 49, pg 1143).

Plane or axis of symmetry

• Different animal types display various symmetry types.

Nervous systems consist of circuits of neurons and supporting cells

• The simplest animals with nervous systems (cnidarians) have nerve nets.
• Examples are provided in relation to organisms' nervous systems.

Nervous systems consist of circuits of neurons and supporting cells

• Starfish have a nerve net in each arm.

Nervous systems consist of circuits of neurons and supporting cells

• Bilaterally symmetrical animals demonstrate cephalization.
• Cephalization is a clustering of sensory organs at the anterior end of the body.
• Some examples of cephalized animals with central nervous systems (CNS) are shown.

Nervous systems consist of circuits of neurons and supporting cells

• Vertebrates have a more complex nervous system.
• The CNS includes the brain and spinal cord.

Central Nervous System

• The brain and spinal cord contain gray matter (neuron cell bodies, dendrites, unmyelinated axons) and white matter (bundles of myelinated axons).

Organization of the Vertebrate Nervous System

• A reflex is an automatic body response to a stimulus.
• The knee-jerk reflex is an example discussed.

Peripheral Nervous System

• The PNS transmits information to and from the CNS, regulating movement and internal environment.
• Afferent neurons carry information to the CNS, while efferent neurons carry information away from the CNS.
• Cranial nerves originate from the brain and serve the head and upper body.
• Spinal nerves originate from the spinal cord and serve the body below the head.

Peripheral Nervous System

• The PNS has a motor system and an autonomic system.
• The motor system controls voluntary movements.
• The autonomic system regulates involuntary processes.
• This involuntary system includes sympathetic and parasympathetic divisions.

Peripheral Nervous System

• A diagram aids in understanding the components and functions of the peripheral nervous system.

The brain

• The vertebrate brain is regionally specialized.
• The brainstem coordinates and conducts information between brain centers.
• The brainstem includes the midbrain, pons, and medulla oblongata.
• Different brain areas control various functions.

The brain

• The midbrain receives and integrates sensory information.
• The pons regulates breathing in the medulla oblongata.
• The medulla contains centers for a range of vital functions.

The brain

• The cerebellum coordinates and checks motor, perceptual, and cognitive functions.
• It's involved in learning and remembering motor skills.

The brain

• The embryonic diencephalon develops into three regions: the epithalamus, thalamus, and hypothalamus.

The brain

• The epithalamus controls cerebrospinal fluid production.
• The thalamus integrates sensory input and relays motor output.
• The hypothalamus regulates homeostasis and survival behaviors.

The brain

• The cerebrum has two cerebral hemispheres.
• Each hemisphere has a cerebral cortex (gray matter), white matter, and basal nuclei.
• The cerebral cortex is the largest part of the human brain.

The brain

• The corpus callosum connects the cerebral cortices.
• The right cerebral cortex controls the left side of the body.

The brain

• The cerebral cortex has four lobes (frontal, temporal, occipital, parietal).
• Each lobe contains sensory and association areas.

The limbic system

• Emotions are generated and experienced through the limbic system, which integrates with other brain regions.
• The limbic system's components include the amygdala, hippocampus, and parts of the thalamus.
• The amygdala is involved in storing emotional experiences as memories.

Memory and Learning

• Learning can occur through new or strengthened neural connections.
• Short-term memory works through the hippocampus.
• Long-term memory storage happens in the cerebral cortex.

Acknowledgements

• The majority of the content and PowerPoint slides are from Campbell's Biology.
• The contribution of Dr. Ramiro Crego is also acknowledged.