Week 10 (Nervous System) Flashcards
(24 cards)
The Nervous System
The nervous system is the master controlling and communicating system of the body.
Controls and coordinates all essential functions of the human body.
Receives, stores, interprets, and responds to information.
Maintains homeostasis by regulating activities of all body systems.
Divisions of the Nervous System
The nervous system is divided into:
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Structural Classification
Central Nervous System (CNS)
Consists of:
Brain
Spinal cord
Functions:
Acts as the integrating and control center.
Interprets sensory information based on past experience and current conditions.
Peripheral Nervous System (PNS)
Part of the nervous system outside of the CNS.
Links all parts of the body.
Carries impulses between sensory receptors, CNS, and effectors.
Consists mainly of:
Nerves that extend from the brain and spinal cord
Cranial nerves: Carry impulses to and from the brain.
Spinal nerves: Carry impulses to and from the spinal cord.
Functions of the Nervous System
Sensory Input
Gathers information through sensory neurons that deliver impulses to the CNS.
Integration
Processes and interprets sensory input using interneurons in the CNS.
Motor Output
Responds to stimuli using motor neurons that carry information from the CNS to effectors (muscles, organs, glands).
Brain
Located within the cranial cavity.
Consists of:
Cerebral hemispheres (Cerebrum)
Diencephalon
Brainstem
Cerebellum
Contains about 85 billion neurons.
Controls all body functions.
Spinal Cord
Long, thin bundle of nerve fibers.
Length in adults: 42–45 cm (16–18 inches).
Protected by the vertebral column.
Functions as a pathway for impulses to and from the brain.
Cerebrum
Largest part of the brain, divided into left and right hemispheres.
Cerebral cortex (outer layer) contains 75% of neural cell bodies.
Responsible for:
Thought processes, intelligence, memory, and judgment.
Sensory perception and motor function.
Diencephalon
Thalamus:
Relay center for sensory information.
Plays a role in consciousness and motor control.
Hypothalamus:
Maintains homeostasis.
Regulates autonomic functions, emotions, and endocrine activity.
Basal Ganglia
Coordinates movement.
Ensures smooth, purposeful motion.
Cerebellum
Second-largest brain structure.
Functions:
Coordinates voluntary and some involuntary movements.
Maintains posture and controls balance.
Brainstem
Consists of:
Midbrain (vision and auditory reflex center).
Pons (relays messages, regulates respiration).
Medulla Oblongata (controls heart rate, breathing, digestion).
Controls reflexes and autonomic functions.
Spinal Cord
Acts as a reflex center and conduction pathway.
Transmits sensory and motor information between the CNS and the body.
Controls automatic reflexes.
Peripheral Nervous System
Includes neurons outside the CNS.
Consists of nerves that branch out from the CNS to the body.
Maintains homeostasis and controls involuntary functions.
Structural Division
Cranial Nerves: 12 pairs.
Spinal Nerves: 31 pairs.
Cervical: 8 pairs
Thoracic: 12 pairs
Lumbar: 5 pairs
Sacral: 5 pairs
Coccygeal: 1 pair
Functional Division
Sensory (Afferent) Division
Transmits impulses from sensory receptors to the CNS.
Motor (Efferent) Division
Transmits impulses from CNS to effector organs (muscles and glands).
Includes:
Somatic Nervous System (voluntary control of skeletal muscles).
Autonomic Nervous System (involuntary control of smooth muscle, cardiac muscle, and glands).
Divisions of Autonomic Nervous System (ANS)
Sympathetic Nervous System (“Fight or Flight”)
Arouses body activity.
Increases heart rate and energy expenditure.
Parasympathetic Nervous System (“Rest and Digest”)
Maintains homeostasis and conserves energy.
Slows heart rate and promotes digestion.
Synapses
Specialized junctions between neurons or between neurons and effector organs.
Types of Synapses
Axodendritic: Between axon and dendrite (most common).
Axosomatic: Between axon and cell body.
Axoaxonic: Between axons of two neurons.
Chemical Synapses
Consist of:
Axon terminal of the presynaptic neuron
Dendrites or cell body of the postsynaptic neuron
Process:
Neurotransmitters are released from vesicles in the presynaptic neuron into the synaptic gap.
Neurotransmitters travel across the gap and bind to receptors on the postsynaptic neuron.
Characteristics:
Indirect transfer of information
Signal transmission delayed (~0.5 ms)
Most common type of synapse
Electrical Synapses
Process:
Flow of ions directly from one neuron to another via gap junctions.
Characteristics:
Direct transfer of information
Signal transmission is nearly instantaneous
Less common than chemical synapses
Excitatory Synapses
Process:
An excitatory neurotransmitter binds to the postsynaptic receptor, leading to depolarization.
Effects:
Sodium (Na⁺) enters the neuron.
The neuron becomes less negative/more positive.
Increases the likelihood of generating an action potential.
Inhibitory Synapses
Process:
An inhibitory neurotransmitter binds to the postsynaptic receptor, leading to hyperpolarization.
Effects:
Chloride (Cl⁻) enters or potassium (K⁺) leaves the neuron.
The neuron becomes more negative/less positive.
Decreases the likelihood of generating an action potential.
Neurotransmitters
50+ Identified. Some examples: Acetylcholine, Norepinephrine, Epinephrine, Dopamine, Serotonin, Glutamate, GABA, Glycine, Substance P.
Synaptic Transmission
Neurotransmitter Synthesis and Storage:
Neurotransmitters are synthesized and stored in synaptic vesicles.
Neurotransmitter Release:
A nerve impulse (action potential) travels down the axon to the axon terminal.
Action potential opens calcium (Ca²⁺) channels, allowing Ca²⁺ to diffuse into the axon bulb.
Calcium influx causes synaptic vesicles to fuse with the presynaptic membrane.
Neurotransmitters are released via exocytosis into the synaptic cleft.
Neurotransmitter Diffusion and Binding:
Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the postsynaptic membrane.
Excitatory neurotransmitters cause sodium (Na⁺) influx, leading to depolarization.
Inhibitory neurotransmitters do not depolarize the postsynaptic membrane.
Action Potential Generation (if excitatory threshold is met):
Neurotransmitter Inactivation:
Neurotransmitters are broken down or reabsorbed to stop the signal.
