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Chapter 14: Coordination and Control 

Table of Contents

Role of the Nervous System:

The nervous system, comprising the brain, spinal cord, and nerves, coordinates and regulates body functions.

Mammalian Nervous System Components:

(a) Central Nervous System (CNS): Consists of the brain and spinal cord.

(b) Peripheral Nervous System (PNS): Includes nerves outside the brain and spinal cord.

https://www.news-medical.net/health/What-is-the-Nervous-System.aspx

  1. Neurons in the Nervous System:
    • Sensory Neurons: Transmit signals from sensory organs to the CNS.
    • Relay Neurons: Transmit signals between neurons in the CNS.
    • Motor Neurones: Carry signals from the CNS to effectors (muscles or glands).
  2. Electrical Impulses:

Electrical impulses travel along neurons, facilitating communication within the nervous system.

  1. Simple Reflex Arcs:
    • Receptor: Detects a stimulus.
    • Sensory Neurons: Transmits the signal to the CNS.
    • Relay Neurone: Coordinates the response.
    • Motor Neurone: Initiates an action by effectors (muscles or glands).
    • Effector: Executes the response.
  2. Reflex Action:

A reflex action is a rapid and automatic response to a stimulus, designed to protect the body from harm.

  1. Synapse Description:

A synapse is a junction between two neurons, facilitating signal transmission.

  1. Synapse Structure:

The synapse includes vesicles containing neurotransmitter molecules, a synaptic gap, and receptor proteins.

Events at a Synapse:

(a) An impulse stimulates the release of neurotransmitter molecules from vesicles into the synaptic gap.

(b) Neurotransmitter molecules diffuse across the gap and bind with receptor proteins.

(c) An impulse is stimulated in the next neurone.

  1. Synaptic Directionality:

Synapses ensure that impulses travel in one direction only, preventing backflow of signals.

Sense Organs 

Definition:

  1. Sense organs are groups of receptor cells that respond to specific stimuli, including light, sound, touch, temperature, and chemicals.
  2. Eye Structures Identification:
    • Cornea: Transparent outer layer refracting light.
    • Iris: Controls pupil size.
    • Pupil: Adjustable opening allowing light entry.
    • Lens: Focuses light onto the retina.
    • Ciliary Muscles: Control lens shape.
    • Suspensory Ligaments: Adjust lens curvature.
    • Retina: Contains light receptors.
    • Fovea: Area of highest receptor density.
    • Optic Nerve: Carries impulses to the brain.
    • Blind Spot: Area with no light receptors.

Eye Part Functions:

(a) Cornea: Refracts light.

(b) Iris: Controls light entering the pupil.

(c) Lens: Focuses light onto the retina.

(d) Ciliary Muscles and Suspensory Ligaments: Control lens shape.

(e) Retina: Contains light receptors, sensitive to different colors.

(f) Fovea: Area with the highest density of light receptors.

(g) Optic Nerve: Transmits impulses to the brain.

  1. Pupil Reflex Explanation:
    • The pupil reflex adjusts to varying light intensity.
    • Circular muscles contract, reducing pupil size in bright light.
    • Radial muscles contract, dilating the pupil in low light.
  2. Accommodation Explanation:
    • Ciliary Muscle Contraction: Allows lens thickening for near vision.
    • Suspensory Ligament Tension: Adjusts lens curvature.
    • Shape of the Lens: Changes to focus light for viewing near or distant objects.
    • Refraction of Light: Enables clear vision at different distances.

Hormones

https://www.news-medical.net/health/What-are-Hormones.aspx

Hormone Definition:

  1. A hormone is a chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs.
  2. Endocrine Glands and Hormones:
    • Adrenal Glands: Produce adrenaline.
    • Pancreas: Produces insulin and glucagon.
    • Pituitary Gland: Produces follicle-stimulating hormone (FSH) and luteinising hormone (LH).
    • Testes: Produce testosterone.
    • Ovaries: Produce estrogen and progesterone.

Role of Adrenaline:

Adrenaline, produced by the adrenal glands, increases blood glucose concentration and heart rate. Situations where this occurs include the “fight or flight” response during stress or emergencies.

  1. Comparison of Nervous and Hormonal Control:
    • Speed of Action:
      • Nervous control is rapid, with almost instantaneous responses.
      • Hormonal control may take longer, as hormones need time to be produced, released, and transported through the bloodstream.
    • Duration of Effect:
      • Nervous control effects are usually short-lived.
      • Hormonal control effects can be prolonged, with a slower onset but a more sustained impact.

Homeostasis 

Definition:

  1. Homeostasis is the maintenance of a constant internal environment within an organism, ensuring optimal conditions for cellular function and overall stability.
  2. Negative Feedback Control:
    • In negative feedback, the body’s responses work to maintain a variable close to a set point.
    • When a deviation from the set point is detected, corrective mechanisms are activated to counteract and bring the system back to the desired range.
    • This continuous feedback loop helps regulate internal conditions and maintain stability.

Skin Components Identification

  • Hairs: Present on the skin.
  • Hair Erector Muscles: Control hair position.
  • Sweat Glands: Produce sweat for cooling.
  • Receptors: Detects temperature changes.
  • Sensory Neurons: Transmit temperature signals.
  • Blood Vessels: Regulate blood flow for temperature control.
  • Fatty Tissue: Provides insulation.

Role of Insulation:

  • Insulation, provided by fatty tissue and fur or hair, helps maintain a constant internal body temperature by reducing heat loss to the surroundings.

Roles in Temperature Regulation:

  • Hypothalamus: Acts as a control centre, regulating temperature by responding to signals from temperature receptors.
  • Temperature Receptors in the Skin: Detect external temperature changes, providing input to the hypothalamus.

Processes Contributing to Temperature Maintenance:

(a) Sweating:

– Function: Releases moisture, facilitating evaporative cooling.

– Effect: Cools the body as sweat evaporates.

(b) Shivering:

– Function: Involuntary muscle contractions generate heat.

– Effect: Raises body temperature.

(c) Contraction of Hair Erector Muscles:

– Function: Raises hairs, trapping a layer of air for insulation.

– Effect: Reduces heat loss.

(d) Vasodilation and Vasoconstriction:

– Vasodilation: Widening of blood vessels to increase blood flow and heat loss.

– Vasoconstriction: Narrowing of blood vessels to decrease blood flow and conserve heat.

Need to Control Blood Glucose Concentration:

  • Maintaining stable blood glucose levels is crucial for providing a constant and adequate energy supply to cells.
  • Fluctuations outside the normal range can lead to health issues, affecting various bodily functions.

Control of Blood Glucose:

  • Liver: Converts excess glucose to glycogen during high blood glucose levels and releases glucose through glycogenolysis when levels are low.
  • Pancreas: Produces insulin to lower blood glucose levels and glucagon to raise them.
  • Insulin: Promotes glucose uptake by cells, storage of excess glucose as glycogen, and inhibits glycogenolysis.
  • Glucagon: Stimulates the release of glucose from glycogen and gluconeogenesis, raising blood glucose levels.

Type 1 Diabetes:

  • Signs:
    • Increased blood glucose concentration.
    • Presence of glucose in urine.
  • Treatment:
    • Administration of insulin to regulate blood glucose levels.
    • Monitoring and managing diet and physical activity to maintain balance.

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