Nervous System Overview Quiz

The Nervous System

• The nervous system is responsible for explaining the functions, divisions, and cells of the system.
• The system contains two major divisions: central and peripheral.
• The central nervous system includes the brain and spinal cord.
• The peripheral nervous system includes neurons and glial cells outside the brain and spinal cord.
• The peripheral nervous system is further divided into sensory and motor divisions.
  • The sensory division carries sensory information to the CNS.
  • The motor division carries messages from the CNS to internal organs, glands, and muscles.
    • The motor division is further divided into somatic and autonomic divisions.
      • Somatic nervous system controls voluntary movements.
      • Autonomic nervous system controls involuntary functions, which further divides into sympathetic and parasympathetic.
        • Sympathetic nervous system prepares the body for emergencies (fight or flight).
        • Parasympathetic nervous system controls the body during non-emergencies.
• The nervous system also has an enteric nervous system, which controls functions within the gastrointestinal tract independently of the brain and spinal cord.
• The brain is the primary control center, consisting of several parts including the cerebrum, cerebellum, brainstem, and diencephalon.
  • The cerebrum is responsible for higher cognitive functions.
  • The cerebellum coordinates balance, posture, and fine motor movements.
  • The brainstem connects the brain to the spinal cord and controls basic life functions.
    • The midbrain controls eye movements and auditory/visual processing.
    • The pons assists in regulating breathing.
    • The medulla oblongata controls vital functions.
  • The diencephalon includes the thalamus, which relays sensory information, and the hypothalamus, which regulates homeostasis, controlling hunger, thirst, sleep, and body temperature. The epithalamus, including the pineal gland, regulates sleep-wake cycles and produces melatonin.
• The spinal cord transmits signals between the brain and the body and controls reflex actions.
• It's a crucial pathway for sending motor instructions and receiving sensory input.
  • The spinal cord is divided into Cervical, Brachial, Lumbar and Sacral plexuses. Each plexus innervates different parts of the body.
• Cranial nerves are 12 paired nerves that emerge directly from the brain and brainstem. They transmit information between the brain and parts of the head, neck, and upper body.
• Olfactory, Optic, Oculomotor, Trochlear, Trigeminal, Abducens, Facial, Vestibulocochlear, Glossopharyngeal, Vagus, Accessory, and Hypoglossal are the 12 cranial nerves. Each has specific function.
• Neurons are the basic units of the nervous system. These cells receive stimuli, conduct action potentials, and transmit signals to other neurons or organs.
• Parts of the neuron include cell body (soma), dendrites, axon, myelin sheath, and axon terminals (synaptic terminals or boutons).
• Glial cells provide support and protection for neurons.
• Cerebrospinal fluid (CSF) is a clear, colorless fluid that surrounds the brain and spinal cord. It cushions the brain, transports nutrients and waste products, regulates intracranial pressure, and supports immune defense.

Cells of Nervous System

• Neurons include multipolar, bipolar, and pseudo-unipolar cells.
  • Multipolar neurons have many dendrites and one axon.
  • Bipolar neurons have one dendrite and one axon.
  • Pseudo-unipolar neurons have one process extending to the periphery and one to the CNS.
• Glial cells include astrocytes, ependymal cells, microglia, oligodendrocytes, and Schwann cells.
  • Astrocytes form blood-brain barrier and help with neural repair.
  • Ependymal cells line ventricles of the brain.
  • Microglia protect the CNS from infection.
  • Oligodendrocytes form myelin sheaths in the CNS.
  • Schwann cells form myelin sheaths in the PNS.
  • Nodes of Ranvier are gaps between myelin sheath segments.
  • Axon terminals are endings of the axon.

Action Potential

• An action potential is a rapid, temporary electrical impulse along a neuron's membrane, allowing communication with other neurons, muscles, or glands.
• Steps of action potential include resting potential, threshold, depolarization, peak, and repolarization, hyperpolarization, refractory period, and return to resting potential.
• Voltage-gated sodium (Na+) channels open, allowing Na+ ions to rush into the cell, causing depolarization.
• When the inside of the cell becomes more positive than outside, the membrane potential increases.
• Voltage-gated potassium (K+) channels open, causing K+ ions to move out of the cell, creating repolarization.
• The sodium-potassium pump helps restore the original ion distribution.
• The refractory period prevents action potential from moving backward along the axon.

Synapse

• A synapse is the junction between two neurons or a neuron and another type of cell (muscle or gland).
• Synapses allow for communication between cells by using chemical messengers called neurotransmitters.
• There are two types of synapses:
  • Chemical synapses (more common) involve the release of neurotransmitters into the synaptic cleft, which bind to receptors on the postsynaptic cell.
  • Electrical synapses involve direct electrical current flow through gap junctions between neurons.
• Steps of chemical synapse include: action potential arrival, neurotransmitter release, binding to receptors, and postsynaptic response, and termination.
• Neurotransmitters binding to receptors cause either an excitatory or inhibitory response in the postsynaptic neuron. Excitatory neurotransmitters depolarize the membrane. Inhibitory neurotransmitters hyperpolarize the membrane.
• Neurotransmitter action is terminated by reuptake into the presynaptic neuron, enzymatic breakdown, or diffusion away from the synapse.

Importance of Synapses

• Synapses allow complex processing, integration of signals, learning, memory, and decision-making.
• Synaptic plasticity allows for strengthening or weakening of synapses over time, underlying learning and the formation of memories.
• Proper functioning depends on the balance of neurotransmitters, otherwise imbalances can lead to neurological disorders, like depression, anxiety, and schizophrenia.

Disorders related to synaptic function

• Some disorders associated with synaptic function include Alzheimer's disease and Parkinson's disease, which involve synaptic dysfunction and imbalance of neurotransmitters.

Test your knowledge about the nervous system, including its major divisions and functions. This quiz covers important concepts related to brain health and neurobiology. Get ready to delve into the complexities of nervous system functioning.