Control and Coordination in Human Body

Control and Coordination

• Control and Coordination: The body is constantly interacting with the surroundings, and within the body, there is a lot of interaction happening, which is why control and coordination are essential.
• The nervous system is responsible for keeping the body informed about the changes happening in the surroundings and within the body.
• Functions of the Nervous System:
  • Keeps the body informed about changes
  • Memorizes and stores information
  • Regulates voluntary and involuntary actions

Stimulus, Response, and Receptors

• Stimulus: Any event or change in the external environment that generates a specific reaction within the body.
• Response: The reaction to a stimulus.
• Receptors: Specialized cells or structures in the body that recognize and respond to stimuli.

Nervous System Structure

• Neurons: The structural and functional units of the nervous system.
• Parts of a Neuron:
  • Cell Body (Cyton or Soma): Contains a prominent nucleus.
  • Dendrites: Receive electric signals.
  • Axon: A long projection that conducts electric signals.
  • Myelin Sheath: A protective fatty layer that surrounds the axon in some cases.
  • Node of Ranvier: Gaps in the myelin sheath.
  • Axon Terminals: The ends of the axon where signals are transmitted.

Neuron Interaction

• Neurons are not directly connected but are closely placed.
• Signal Transmission:
  • Dendrites receive electric signals.
  • Signals pass through the cyton, axon, and axon terminals.
  • Signals are transmitted to the next neuron through the synapse.

Important Terms

• Impulse: A sudden electric signal that passes through the neuron.

• Signal: A colloquial term for the electric signals transmitted through the neuron.

• Myelinated Axons: Axons surrounded by a myelin sheath.

• Nurilemma (Axolemma): A thin layer that protects axons.### Neurons and Signal Transmission

• A neuron is a single cell that transmits information.

• The structure of a neuron consists of:

• Dendrites (receive signals)

• Cell body (contains nucleus)

• Axon (transmits signals)

• Axon terminals (release neurotransmitters)

Myelin Sheath

• A myelin sheath is a fatty tissue that provides insulation to the axon.
• It is composed of fatty tissue and covers the axon.
• The myelin sheath helps in faster transmission of signals.

Synapse

• A synapse is a fine gap between two neurons.
• It is the gap between the axon terminal of one neuron and the dendrites of another neuron.
• Neurotransmitters are released from the axon terminal into the synapse and bind to receptors on the dendrites of the next neuron.

Neurotransmitters

• Neurotransmitters are chemicals released from the axon terminal that help transmit information.
• Examples of neurotransmitters include acetylcholine.
• Neurotransmitters transmit information from one neuron to another.

Signal Transmission

• Electric signals are transmitted through the neuron, but there is a chemical signal at the synapse.
• The signal is transmitted from the dendrites to the cell body to the axon to the axon terminals.
• The signal is then released as neurotransmitters into the synapse.

Types of Neurons

• Sensory neurons transmit information from sense organs to the brain or spinal cord.
• Motor neurons transmit information from the brain or spinal cord to muscles or glands.
• Relay neurons (or interneurons) connect sensory and motor neurons.

Nerves and Ganglia

• A nerve is a bundle of axons from multiple neurons.
• Ganglia are collections of cell bodies that form a structure.
• Sensory neurons together make up sensory nerves, and motor neurons together make up motor nerves.

Central Nervous System (CNS)

• The CNS consists of the brain and spinal cord.
• It is responsible for controlling and coordinating various activities in the body.

Voluntary and Involuntary Actions

• Voluntary actions are actions that can be controlled, such as walking or talking.
• Involuntary actions are actions that cannot be controlled, such as heartbeat or breathing.

Reflex Action

• Reflex action is an involuntary and instantaneous reaction to a stimulus.
• Examples of reflex actions include touching a hot object or a sharp object.
• Reflex action is different from reflex arc.

Reflex Arc

• Reflex arc is the shortest route taken by the electrical signal from the receptor to the effector.
• It is the path taken by the signal from the receptor to the CNS and then to the effector.
• The reflex arc involves the receptor, sensory neuron, CNS, relay neuron, and motor neuron.### Reflex Action and Reflex Arc
• Reflex action: an involuntary and nearly instantaneous response to a stimulus
• Reflex arc: the path taken by an impulse within the body to carry out the action
  • Includes: receptor, sensory neuron, central nervous system, motor neuron, and effector (muscle or gland)

Central Nervous System (CNS)

• Main parts: brain and spinal cord
• Protected by bony structures (cranium and vertebral column) and meninges (membrane-like structure)
• Functions:
  • Brain:
    • Controls voluntary actions
    • Processes sensory information
    • Site of intelligence and memory
  • Spinal cord:
    • Relays information between brain and peripheral nervous system
    • Coordinates reflexes

Brain Structure

• Divided into three main parts: forebrain, midbrain, and hindbrain
• Forebrain:
  • Largest part of the brain (2/3)
  • Includes: cerebrum, thalamus, and hypothalamus
  • Functions: receives and processes sensory information, controls voluntary actions, and regulates body temperature, hunger, and sleep
• Midbrain:
  • Acts as a relay point for sensory impulses
  • Regulates visual and auditory processing
  • Controls reflexes of the eye
• Hindbrain:
  • Includes: cerebellum, pons, and medulla oblongata
  • Functions: regulates involuntary actions (breathing, heart rate, blood pressure), controls precision involuntary actions, and coordinates muscular activity

Peripheral Nervous System (PNS)

• Includes all nerves that come out of the CNS
• Divided into two main parts: cranial and spinal
• Cranial nerves: 12 pairs that emerge from the brain
• Spinal nerves: 31 pairs that emerge from the spinal cord
  • Regulate involuntary functions and transmit impulses between CNS and peripheral organs

Other Important Facts

• Cerebrospinal fluid (CSF): a fluid between the meninges that absorbs shocks, keeps the CNS moist, and supplies food and oxygen
• Grooves and ridges in the brain: increase the surface area for neurons and axons
• Cerebrum has two hemispheres connected by the corpus callosum for coordinated movement and cognitive functions
• Hypothalamus regulates body temperature, hunger, and thirst
• Medulla oblongata regulates involuntary actions (heart rate, blood pressure, salivation)

Control and Coordination

• Control and coordination are essential for the body to interact with its surroundings and itself.
• The nervous system is responsible for keeping the body informed about internal and external changes.

Nervous System Functions

• Keeps the body informed about changes
• Memorizes and stores information
• Regulates voluntary and involuntary actions

Stimulus, Response, and Receptors

• A stimulus is an event or change that generates a specific reaction within the body.
• A response is the reaction to a stimulus.
• Receptors are specialized cells or structures that recognize and respond to stimuli.

Nervous System Structure

Neurons

• Neurons are the structural and functional units of the nervous system.
• A neuron consists of:
  • Cell body (cyton or soma) containing a prominent nucleus
  • Dendrites that receive electric signals
  • Axon that conducts electric signals
  • Myelin sheath (in some cases) that protects the axon
  • Node of Ranvier (gaps in the myelin sheath)
  • Axon terminals where signals are transmitted

Neuron Interaction

• Neurons are closely placed but not directly connected.
• Signal transmission occurs through:
  • Dendrites receiving electric signals
  • Signals passing through the cyton, axon, and axon terminals
  • Signals transmitted to the next neuron through the synapse

Important Terms

• An impulse is a sudden electric signal that passes through the neuron.
• A signal is a colloquial term for the electric signals transmitted through the neuron.
• Myelinated axons are axons surrounded by a myelin sheath.
• Nurilemma (axolemma) is a thin layer that protects axons.

Neurons and Signal Transmission

• A neuron transmits information through its structure:
  • Dendrites receive signals
  • Cell body contains nucleus
  • Axon transmits signals
  • Axon terminals release neurotransmitters

Myelin Sheath

• A myelin sheath is a fatty tissue that provides insulation to the axon.
• It helps in faster transmission of signals.

Synapse

• A synapse is a fine gap between two neurons.
• Neurotransmitters are released from the axon terminal into the synapse and bind to receptors on the dendrites of the next neuron.

Neurotransmitters

• Neurotransmitters are chemicals released from the axon terminal that help transmit information.
• Examples of neurotransmitters include acetylcholine.

Signal Transmission

• Electric signals are transmitted through the neuron, but there is a chemical signal at the synapse.
• The signal is transmitted from the dendrites to the cell body to the axon to the axon terminals.

Types of Neurons

• Sensory neurons transmit information from sense organs to the brain or spinal cord.
• Motor neurons transmit information from the brain or spinal cord to muscles or glands.
• Relay neurons (or interneurons) connect sensory and motor neurons.

Nerves and Ganglia

• A nerve is a bundle of axons from multiple neurons.
• Ganglia are collections of cell bodies that form a structure.

Central Nervous System (CNS)

• The CNS consists of the brain and spinal cord.
• It is responsible for controlling and coordinating various activities in the body.

Voluntary and Involuntary Actions

• Voluntary actions are actions that can be controlled, while involuntary actions cannot be controlled.