Ascending Sensory Tracts
1. Spinothalamic Tract
● Type: Sensory
● Goes from thalamus to cortex
● Carries: Pain and temperature
● Crossover: Immediately after entering spinal cord
2. Spinoreticular Tract
● Type: Sensory
● Carries: Pain signals resulting from tissue injury
● Crossover: As soon as it enters the spinal cord
3. Spinocerebellar Tract
● Type: Sensory
● Carries: Muscle stretch and body position
● Location: Transmits information about muscle and joint position
● Crossover: Does NOT crossover
Descending (Motor) Tracts
1. Corticospinal Tract
● Type: Motor
● Carries: Signals from the cortex
● Crossover: Medulla oblongata (pyramidal decussation)
● Controls fine and precise movements
● Goes to skeletal muscles
Signal Transmission
● Receptor → Control Center (Brain) → Effector
● ATE to remember: Affector → Brain → Effector
● Effectors: Smooth muscles, cardiac muscles, skeletal muscles, glands
● Pathway Types:
● Afferent (sensory) = Incoming signals
● Efferent (motor) = Outgoing signals
Neuron Characteristics
● Dendrites: Primary site for receiving signals from other neurons
● Axon Hillock: Trigger zone
● Threshold for Action Potential: -55 charge
● Myelin functions to speed up an action potential and is made up of fat
● In Multiple Sclerosis (MS) myelin is missing
● ATP is required for actin and myosin separating
● Actin and myosin not separating is called rigor mortis (death)
, Nervous System Classifications
Sensory Types
● Visceral Sensory: Involves internal organs
● Somatic Sensory: Involves bones, joints, muscles, and skin
Motor Types
● Visceral Motor: Motor going to internal organs
● Sympathetic (Fight or Flight):
● Runs on thoracic nerves (T1 to T12)
● Accelerates heart beat
● Stops digestion and urination
● Parasympathetic (Calming):
● Runs on vagus nerve (#10)
● Slows heart rate
● Stimulates digestion and urinary systems
● Somatic Motor: Motor going to skeletal muscles
Nerve Cell Groupings
● CNS:
● Axon group: Tract
● Cell body group: Nuclei
● PNS:
● Axon group: Nerve
● Cell body group: Ganglion
Central Nervous System (CNS) Glial Cells
1. Astrocytes: Support and nourish neurons
2. Oligodendrocytes: Produce myelin for nerve insulation
3. Microglia: Immune defense cells
4. Ependymal cells: Line brain ventricles and spinal cord central canal
Peripheral Nervous System (PNS) Glial Cells
1. Schwann cells: Produce myelin for peripheral nerve insulation
2. Satellite cells: Support and protect neuron cell bodies
Polarizations
1. Depolarization: Sodium channels open, sodium enters cell, charge becomes more positive
2. Repolarization: Potassium channels open, potassium leaves the cell
3. In neurons: Hyperpolarization occurs NOT in skeletal muscles (potassium channels stay
open longer)
4. The primary site on the neuron for receiving signals from other neurons is the dendrites
5.
6. The axon hillock is the trigger zone
7. Action potential only occurs in nerves and muscles
1. Spinothalamic Tract
● Type: Sensory
● Goes from thalamus to cortex
● Carries: Pain and temperature
● Crossover: Immediately after entering spinal cord
2. Spinoreticular Tract
● Type: Sensory
● Carries: Pain signals resulting from tissue injury
● Crossover: As soon as it enters the spinal cord
3. Spinocerebellar Tract
● Type: Sensory
● Carries: Muscle stretch and body position
● Location: Transmits information about muscle and joint position
● Crossover: Does NOT crossover
Descending (Motor) Tracts
1. Corticospinal Tract
● Type: Motor
● Carries: Signals from the cortex
● Crossover: Medulla oblongata (pyramidal decussation)
● Controls fine and precise movements
● Goes to skeletal muscles
Signal Transmission
● Receptor → Control Center (Brain) → Effector
● ATE to remember: Affector → Brain → Effector
● Effectors: Smooth muscles, cardiac muscles, skeletal muscles, glands
● Pathway Types:
● Afferent (sensory) = Incoming signals
● Efferent (motor) = Outgoing signals
Neuron Characteristics
● Dendrites: Primary site for receiving signals from other neurons
● Axon Hillock: Trigger zone
● Threshold for Action Potential: -55 charge
● Myelin functions to speed up an action potential and is made up of fat
● In Multiple Sclerosis (MS) myelin is missing
● ATP is required for actin and myosin separating
● Actin and myosin not separating is called rigor mortis (death)
, Nervous System Classifications
Sensory Types
● Visceral Sensory: Involves internal organs
● Somatic Sensory: Involves bones, joints, muscles, and skin
Motor Types
● Visceral Motor: Motor going to internal organs
● Sympathetic (Fight or Flight):
● Runs on thoracic nerves (T1 to T12)
● Accelerates heart beat
● Stops digestion and urination
● Parasympathetic (Calming):
● Runs on vagus nerve (#10)
● Slows heart rate
● Stimulates digestion and urinary systems
● Somatic Motor: Motor going to skeletal muscles
Nerve Cell Groupings
● CNS:
● Axon group: Tract
● Cell body group: Nuclei
● PNS:
● Axon group: Nerve
● Cell body group: Ganglion
Central Nervous System (CNS) Glial Cells
1. Astrocytes: Support and nourish neurons
2. Oligodendrocytes: Produce myelin for nerve insulation
3. Microglia: Immune defense cells
4. Ependymal cells: Line brain ventricles and spinal cord central canal
Peripheral Nervous System (PNS) Glial Cells
1. Schwann cells: Produce myelin for peripheral nerve insulation
2. Satellite cells: Support and protect neuron cell bodies
Polarizations
1. Depolarization: Sodium channels open, sodium enters cell, charge becomes more positive
2. Repolarization: Potassium channels open, potassium leaves the cell
3. In neurons: Hyperpolarization occurs NOT in skeletal muscles (potassium channels stay
open longer)
4. The primary site on the neuron for receiving signals from other neurons is the dendrites
5.
6. The axon hillock is the trigger zone
7. Action potential only occurs in nerves and muscles
