Lecture One

• Types of Signaling:

  • Autocrine: substance secreted by a cell and acting on surface receptors of the same cell
  • Paracrine: substance secreted by a cell and acting on adjacent cells
  • Endocrine: producing secretions (typically hormones) that are distributed through the body by the bloodstream
  • Direct Signaling: uses gap junctions connecting cells to pass secretions (common in the heart)
• Nervous System Signaling:

  • Relatively fast
  • Very localized
  • Control short term events like muscle contractions or a thought
• Endocrine System Signaling:

  • Relatively slow
  • Not as localized
  • Control longer term events involving many tissues such as metabolism, growth, reproduction
• Neurons can innervate the endocrine system

  The endocrine system can act upon neurons
• Nervous System Organization:

  • Central Nervous System (CNS): Brain, Spinal cord
  • Peripheral Nervous System (PNS): Nerves, Ganglia
  • Ganglia: collection of neurons in vertebrates in the PNS, in insects could be centralized
  • Nuclei: collection of neurons in CNS
  • Nerves: bundle of axons in PNS
  • Tract: bundle of axons in CNS
  • Interneurons: reside entirely within CNS, don’t project very far
  • Sensory Neurons: bring information to CNS, generally in PNS
  • Motor Neurons: carry information out of the CNS, project out into PNS, mostly within CNS
• Peripheral nervous system includes:

  • Autonomic: controls self-regulated actions like breathing
  • Sympathetic: responsible for arousing responses
  • Parasympathetic: responsible for calming responses
  • Somatic: controls voluntary movements of skeletal muscles
• Central nervous system consists of the Vertebrate Central Nervous System:

  • Brain is protected by the skull
  • Spinal cord is protected by the vertebral column
  • Gray matter consists of cell bodies, synapses, and unmyelinated neural processes
  • White matter consists of tracts of myelinated axons
  • Segmental nerves in the PNS connect to the spinal cord dorsal and ventral roots
  • Ventral roots lead from the spinal cord out
  • Dorsal roots come from the PNS to the spinal cord
• Vertebrate Brain includes:

  • All but the telencephalon is considered in the reptilian brain
  • Forebrain: Telencephalon, Diencephalon
  • Midbrain: Mesencephalon
  • Hindbrain: Metencephalon, Myelencephalon
• Autonomic vs. Somatic Nervous System:

  • Somatic:
  • Nerve contacts effector directly
  • Voluntary system controlling skeletal muscles
  • Usually under conscious control
  • Autonomic:
  • Parasympathetic (craniosacral division) synapses at parasympathetic ganglion before reaching effector
  • Consists of pre- and post-ganglionic neurons
  • During stress or physical activity, known as "Fight or flight"
  • Sympathetic (thoracolumbar division) synapses at sympathetic ganglion before reaching effector
  • Consists of pre- and post-ganglionic neurons
• • During rest, known as "Resting and digesting"
  • Both systems are used for:
  • Smooth muscle throughout the body
  • Exocrine glands (pancreas)
  • Endocrine glands (adrenal glands)
  • Heart pacemaker
• Enteric Division is the intrinsic nervous system of the gastrointestinal tract
• Enteric division receives input from the vagus and spinal nerves
• Enteric division receives input from the sympathetic and parasympathetic divisions
• Enteric division contains thousands of small ganglia within the walls of the system
• Considered a "second brain"
• Ganglia are found in the outer muscle layers (myenteric plexus) and deeper in the submucosal layer (submucosal plexus)
• Reticular Theory suggests the brain is a single continuous network, while Neuron Doctrine states that all neurons are separate entities
• Types of Neurons:

  • Afferent neurons convey information to a neuron (usually dendrites)
  • Efferent neurons convey information from a neuron (mainly axons)
  • Interneurons make connections within regions
• Functional Zones of Neurons:

  • Signal reception involves dendrites and part of the cell body
  • Signal integration occurs at the axon hillock, initiating action potentials
  • Signal conduction happens in the axon, conducting action potentials to axon terminals
  • Signal transmission occurs at the axon terminal, where neurotransmitter release transmits a signal to the target cell
• Dendrites:

  • Have a rough surface
  • Not insulated
  • Bring information to the neuron
  • Each neuron has many dendrites
• Axons:

  • Have a smooth surface
  • Usually insulated with myelin
  • Take information away from the cell
  • Each neuron has one axon with many terminals that end in axonal boutons
• Axonal Transport:

  • Kinesin is responsible for anterograde transport away from the cell body
  • Dynein is responsible for retrograde transport toward the cell body
• Cell Body:

  • Also known as soma
  • Contains the nucleus
• Glial Cells (Neuroglia):

  • Schwann Cells form myelin sheaths in the peripheral nervous system
  • Astrocytes transport nutrients to neurons, remove debris, and regulate space around synapses
  • Oligodendrocytes form myelin sheaths in the central nervous system and may wrap around more than one neuron
  • Microglial Cells provide active immune defense and have a role in neurodegeneration
  • Ependymal Cells line fluid-filled cavities of the brain and circulate cerebrospinal fluid
• • Radial Glia Cells are important progenitor cells during neurogenic phase development and serve as scaffolds for neuronal migration in the cerebral and cerebellar cortices
• Functions of Glial Cells:

  • Surround neurons and hold them in place
  • Supply nutrients and oxygen to neurons
  • Insulate neurons
  • Destroy pathogens
  • Speed up axonal conduction
  • Assist with neurotransmitter release at synapses