BIOL 1160 Week 4: Nervous System

Nervous System

• The Central Nervous System (CNS) and Peripheral Nervous System (PNS) are two distinct parts of the nervous system
• The CNS includes the brain and spinal cord, while the PNS includes nerves and ganglia
• Information processing and organization in the nervous system involve the transmission of signals between neurons through synapses

Neuron Structure

• A typical neuron consists of:
  • Dendrites: receive signals from other neurons
  • Cell body: contains the nucleus and most of the cell's organelles
  • Axon: carries signals away from the cell body
  • Synaptic end bulb: releases neurotransmitters into the synapse
  • Axon terminal: end of the axon where signaling occurs
  • Axon collateral: branch of the axon that forms synapses with other neurons

Synapse Anatomy

• A synapse consists of:
  • Presynaptic neuron: releases neurotransmitters
  • Postsynaptic neuron: receives neurotransmitters
  • Synaptic vesicles: contain neurotransmitters
  • Neurotransmitters: chemical signals transmitted between neurons
  • Receptor: receives neurotransmitters on the postsynaptic neuron
  • Synaptic end bulb: releases neurotransmitters from the presynaptic neuron

Electrical Signaling

• Resting potential: negative electrical potential of a neuron at rest
• Hyperpolarization: increase in negative electrical potential
• Depolarization: decrease in negative electrical potential
• Threshold: minimum depolarization required to generate an action potential
• Action potential: rapid depolarization and repolarization of a neuron
• Transport proteins involved in action potential: sodium-potassium pump, sodium channels, potassium channels

Action Potential Graph

• An action potential graph shows the rapid depolarization and repolarization of a neuron
• Events of an action potential:
  • Depolarization to threshold
  • Rapid depolarization (action potential)
  • Repolarization
  • Hyperpolarization

Traveling Action Potential

• An action potential travels along an axon through the propagation of depolarization

Neuron Types

• Multipolar neurons: have multiple dendrites and one axon
• Bipolar neurons: have two processes (one dendrite and one axon)
• Unipolar neurons: have one process that serves as both dendrite and axon
• Sensory neurons: transmit signals from sensory receptors to the CNS
• Motor neurons: transmit signals from the CNS to effectors
• Interneurons: transmit signals between neurons within the CNS

Neuroglia

• Neuroglia: non-neuronal cells that support and maintain neurons
• Types of neuroglia:
  • Astrocytes: provide nutrient and oxygen support
  • Oligodendrocytes: form myelin in the CNS
  • Microglia: immune cells that protect the CNS
  • Schwann cells: form myelin in the PNS
  • Satellite cells: provide support and maintenance in the PNS

Myelination

• Myelination: the process of forming a myelin sheath around an axon to increase conduction speed
• Myelin is formed by oligodendrocytes in the CNS and Schwann cells in the PNS

Nervous System Terms

• Ganglia: clusters of nerve cells outside the CNS
• Nucleus: a cluster of nerve cells within the CNS
• Nerve: a bundle of axons outside the CNS
• Tract: a bundle of axons within the CNS
• White matter: regions of the CNS composed of myelinated axons
• Gray matter: regions of the CNS composed of neuron cell bodies and dendrites

Reflex Arc

• A reflex arc consists of:
  • Sensory receptors: detect stimuli
  • Sensory neuron: transmits signals from sensory receptors to the CNS
  • Dorsal root ganglion: contains cell bodies of sensory neurons
  • Interneuron: transmits signals within the CNS
  • Somatic motor neuron: transmits signals from the CNS to effectors
  • Skeletal muscle effector: responds to motor neuron signals

Cerebrum

• The cerebrum is the largest part of the brain, responsible for higher-level functions
• The cerebrum is divided into four lobes:
  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe

Endocrine System

• The anterior pituitary gland receives signals from the hypothalamus and regulates hormone secretion
• The posterior pituitary gland stores and releases hormones produced by the hypothalamus
• Neurosecretory cells in the hypothalamus produce hormones that regulate the anterior and posterior pituitary glands