فسيولوجيا الخلايا العصبية

General Information

• This document appears to be a biology textbook or study guide for 12th-grade science students in an Arabic-speaking country.
• It covers the topic of the nervous system (including neurons, nerve signals, and reflexes) and its interaction with the endocrine system.
• The document also includes information on the structure and function of the brain including the cerebrum, cerebellum and brainstem, and various other relevant topics like neurotransmitters and reflexes.

Nervous System Structure and Function

• The nervous system is the central control system for most sensory and motor processes in the body.
• It uses electrochemical signals to transmit messages.
• The nervous system works in coordination with the endocrine system, which uses chemical signals.
• The central nervous system (CNS) comprises the brain and spinal cord.
• The peripheral nervous system (PNS) is made up of sensory and motor neurons.
• The PNS is further divided into the somatic (voluntary) and autonomic (involuntary) systems.
• The somatic nervous system controls voluntary muscle movements, while the autonomic nervous system controls involuntary processes like heart rate and digestion

Nervous Tissue and Cells

• Neurons are specialized cells that transmit information.
• The different parts of a neuron include dendrites, cell body, the axon, and axon terminals.
• Neurons are categorized by their shape and function.
• Motor neurons transmit signals from the CNS to effectors (muscles and glands), while sensory neurons transmit signals from sensory receptors to the CNS.
• Interneurons connect sensory and motor neurons within the CNS.
• Glial cells support and protect neurons.
• Examples of glial cells include Schwann cells which produce myelin sheaths around axons, increasing the speed of nerve impulses.

Nerve Signal Transmission

• Nerve signals travel as electrochemical impulses.
• The resting potential of a neuron is the difference in electrical charge across its membrane.
• In a resting state, the inside of a neuron is negatively charged, with a high concentration of potassium ions (K+) and a low concentration of sodium ions (Na+).
• Stimuli above a certain threshold potential trigger an action potential, resulting in a rapid change in membrane permeability.
• Depolarization occurs when sodium ions (Na+) enter the neuron, making the inside positive.
• Repolarization happens when potassium ions (K+) leave the neuron, restoring the negative charge inside
• The nerve impulse jumps along the myelinated parts of the axon (saltatory conduction) and slower along non-myelinated axons.
• Neurotransmitters are released at the synapse to transmit signals between neurons.

Reflexes and Involuntary Actions

• Simple reflexes are involuntary responses to stimuli.
• The reflex arc is the pathway involved in a reflex action.
• Sensory receptors detect a stimulus.
• Sensory neurons carry the impulse to the spinal cord.
• Interneurons in the spinal cord process the signal and activate motor neurons.
• Motor neurons transmit the signal to effectors, producing the response.
• Complex reflexes involve the brain.

Brain and Endocrine System Interaction

• The brain is the control center of the body.
• It has different lobes with specific functions.
• The major regions include the cerebrum, cerebellum, and brain stem.
• The cerebrum is responsible for conscious activities and thought.
• The cerebellum is essential for coordination and balance.
• The brain stem controls vital involuntary functions such as breathing and heart rate.
• The endocrine system is a network of glands secreting hormones into the bloodstream.
• The brain's hypothalamus and pituitary regulate many endocrine functions, including those controlling growth and metabolism.
• The nervous system and endocrine system work together to maintain homeostasis.

Neurotransmitters and their function

• Neurotransmitters are chemical messengers that transmit signals across synapses, allowing communication between neurons or neurons to other target cells such as muscles and glands.
• The action of neurotransmitters is typically fast, allowing for rapid responses to stimuli.
• Different neurotransmitters have distinct functions.