Topic 6: Responding to the Environment - Humans Notes

Life Processes in Plants and Animals: Responding to the Environment - Humans

Topic 6 Overview: Responding to the Environment - Humans

  • Focus on how humans respond to their environment through:
    • Nervous system
    • Endocrine system

Unit 1: Humans have two systems - nerves and hormones

  • 1.1 Homeostatic Control Systems:
    • The human body maintains homeostasis through the nervous and endocrine systems.
    • Nervous System:
      • Includes the brain, spinal cord, and nerves.
      • Information transmitted via electrical impulses along nerves.
      • Nerves link the body to the brain and spinal cord.
    • Endocrine System:
      • Composed of endocrine glands.
      • Controls metabolic activities by secreting hormones directly into the bloodstream.
      • Hormones travel to target organs (specific groups of cells, glands, or organs).
    • Two systems work together to coordinate activities and responses.
    • Table 6.1 compares nervous and endocrine systems:
      • Nervous System:
        • Controls muscles and glands using electrical impulses.
        • Electrical impulses cause quick, immediate responses in effector organs (muscles or glands).
      • Endocrine System:
        • Utilizes hormones that travel in the blood to control metabolic activities.
        • Hormones target specific groups of cells, glands, or organs (target organs).
        • Responses are slow and long-lasting.

Unit 2: Human Nervous System

  • 2.1 Reactions to Stimuli:

    • Humans react to changing internal or external stimuli using a complex nervous system.
    • Stimuli: Things in the environment that a person can sense and respond to (internal or external).
      • Examples: Soccer ball, field, players, audience, and external factors like smells or weather.
    • Nervous system helps prioritize and focus on specific stimuli.
    • Reactions: Muscle movement, cellular energy release, breathing rate changes.

  • 2.2 Central Nervous System (CNS):

    • Made up of delicate nervous tissue.
    • Protected by:
      • Skull (cranium) surrounding the brain.
      • Vertebral column housing the spinal cord.
      • Meninges (three membranes enclosing and protecting CNS tissue).
        • Pia mater: Innermost membrane with rich blood supply.
        • Arachnoid mater: Middle membrane with sub-arachnoid space filled with cerebrospinal fluid (CSF).
          • Functions of CSF: Acts as a cushion, nourishes nerve cells, removes waste products, maintains constant pressure, and prevents drying out.
        • Dura mater: Tough, durable outer membrane.
    • Brain:
      • Enlarged upper part of the spinal cord.
      • Grey matter: Outer layer of the brain containing mostly cell bodies.
      • White matter: Inner section of the brain and spinal cord consisting mostly of axons (nerve fibers) with myelin sheaths.
        • Myelin sheaths: Fatty layers insulating neurons and allowing for high-speed impulse travel.
      • Ventricles: Hollow spaces/chambers within the brain filled with CSF.
    • Brain Structures (Figure 6.4):
      • Cerebrum
      • Corpus callosum
      • Ventricle
      • Grey matter
      • White matter
      • Cerebellum
      • Spinal cord
      • Hypothalamus
      • Pituitary gland
      • Medulla oblongata

  • Cerebrum and Corpus Callosum:

    • Cerebrum: Largest part of the brain. Consists of two hemispheres (left and right) connected by the corpus callosum.
      • Functions:
        • Determines emotions, personality, intelligence, problem-solving, and speech.
        • Interprets sensory impulses (sight, sound, touch).
        • Controls voluntary muscular movement.
    • Corpus Callosum: Thick band of nerve fibers (white matter) allowing communication between the cerebrum's hemispheres.

  • Cerebellum:

    • Lies below the cerebrum; hemispheres connected by tissue strip.
      • Inside cerebellum, white matter branches form the arbor vitae.
      • Functions:
        • Coordinates voluntary muscular movement.
        • Helps maintain posture and balance.

  • Medulla Oblongata:

    • Forms lowest part of the brain stem.
      • Grey matter inside in H-shape.
      • Has central canal filled with CSF.
      • Similar in structure to spinal cord.
      • Functions:
        • Maintains vital body functions (breathing, blood pressure, heart rate).
        • Contains nerve fibers that cross over (left brain controls right body, vice versa).

  • Spinal Cord:

    • Long, thin, tubular structure extending from the medulla oblongata.
      • Internal structure similar to medulla oblongata.
      • Functions:
        • Connects peripheral nervous system (PNS) to the brain.
        • Responsible for simple reflexes.

  • Activity 2:

    • Examine a cross-section of spinal cord to observe the white and grey matter

  • Activity 3: Observe the structure and regions of a sheep brain

  • 2.3 Peripheral Nervous System (PNS):

    • Made of nervous tissue outside of the CNS.
    • Sensory nerves carry information from internal and external receptors to brain and spinal cord.
    • Motor nerves carry information from the CNS to effectors (muscles and glands).
    • Consists of:
      • Somatic nervous system: Receives information from receptors, controls voluntary muscle responses.
      • Autonomic nervous system (ANS): Controls involuntary muscles and regulates glands.
        The main function of the PNS is to link the CNS to the body's receptors and effectors.

  • 2.4 Autonomic Nervous System (ANS):

    • Controls involuntary reflex actions of organs.
    • Composed of the sympathetic and parasympathetic nervous systems.
      • Sympathetic Nervous System:
        • Controls activities that increase energy use (fight-or-flight response).
        • Works with adrenaline.
      • Parasympathetic Nervous System:
        • Controls activities that decrease energy use (rest-and-digest response).
        • Active during relaxation or when the body returns to normal post-stress.
          Table 6.2: Effects of ANS on the body

  • 2.5 Nerves - Structure of a Nerve:

    • Basic unit: Nerve cell or neuron.
    • Nerves are made up of interconnecting neurons and supporting cells.
    • Structure:
      • Epineurium: Connective tissue layer surrounding the nerve.
      • Perineurium: Encloses bundles of neurons (nerve cells).
      • Endoneurium: Delicate connective tissue layer surrounding individual neurons within the bundle.

  • Nerve Tissue - Types of Neurons:

    • Neurons vary in size and shape.
      • Sensory (unipolar) neuron:
        • Single strand/process extends from cell body (containing nucleus).
        • Cell bodies located outside CNS.
        • Known as afferent neurons.
        • Receptors/sense organs transmit information as nerve impulses to CNS.
          Figure 6.9
      • Motor (multipolar) neuron:
        • Many strands/processes extend from cell body.
        • Cell body located inside CNS.
        • Known as efferent neurons.
        • Transmit nerve impulses from CNS to effectors (muscles/glands).
          Figure 6.10
      • Bipolar neuron:
        • Two strands/processes extending from the cell body.
        • Receptors for taste, smell, hearing, and sight.
          Figure 6.11

  • The structure of sensory neuron and motor neurons

  • 2.6 Reflex Arc:

    • Reflex actions: Fast, involuntary responses.
      • Part of the peripheral nervous system.
    • Reflex arc allows for quick involuntary response of muscle/gland due to receptor stimulation.
    • Functional unit of nervous system.
    • Neuron is the structural unit.

  • Simple Reflex Arc Structure:

    • Neuron pathway carrying impulses from receptor to effector.
    • Flow (Fig 6.14):
      • Stimulus -> Receptor -> Sensory Neuron -> Coordinator (CNS/Spinal Cord) -> Motor Neuron -> Effector -> Response
        Function & Significance

  • Protects the body from dangerous situations

  • Reflex arcs protect the body from dangerous situations: (Fig 6.15).:
    * Prick finger -> Pain receptors detect -> Sensory neuron carries impulse to spinal cord (dorsal root) -> Sensory neuron synapses with interneuron -> Interneuron synapses with motor neuron (ventral root) -> Motor neuron carries impulse to effector (muscle) -> Muscle contracts, finger withdrawn.

  • Activity 4: - Observe and draw a neuron

  • 2.7 Transmission of Nerve Impulses:

    • Nerve impulse travels as electrical signal along neuron surface membrane.
      • From dendrite, through cell body, along axon to synaptic knob.
    • Neurons lie end-to-end with synapse (tiny gap) between them. Figure 6.16
      • Impulses travel over the synapse through:
        • Electrical impulse reaching terminal knob.
        • Vesicles producing neurotransmitters.
        • Vesicles moving to membrane, releasing neurotransmitters into synapse.
          *Neurotransmitters at surface membrane, attach themselves to to the neuron's dentride.
          *Significant for the synapses:
    • Ensures impulses travel in one directions
      • Nerve impulse can speed up, slow down or blocked

  • The human body can naturally control nerve impulse by releasing hormones such as insulin and drugs to treat diseases and infections.
    *Formal assessment is required:

  • Activity 5: Design an imvestigation to determine reaction times.

  • Table 6.3, table to convert the distance the ruler dropped to reaction time

Unit 3: Disorders of the Nervous System

  • 3.1 Alzheimer's Disease:

    • Progressive, degenerative brain disease leading to dementia.
    • Causes:
      • Old age, family history (genetic link), head injury, lifestyle factors (lack of exercise, unhealthy diet).
    • Prevention:
      • Avoid smoking, moderate alcohol consumption, social activity, intellectual stimulation.
    • Symptoms:
      • Difficulty finding words, memory loss, understanding speech, performing daily activities, personality/mood changes.
    • Treatment:
      • No cure; drugs treat symptoms (thinking, memory, perception) temporarily.
      • Eventually requires full-time care.

  • 3.2 Multiple Sclerosis (MS):

    • Affects central nervous system (CNS).
      • Sclerosis: Hardened tissue/scars.
    • Breakdown of myelin sheath covering neurons leads to scars interfering with nerve transmission
      Healthy neuron: damaged and scarred myelin sheath
      Figure 6.19 Damaged Neuron

  • Causes (MS): The immune or defensed system attacks the myelin sheath of the neurons transmission.
    *thought that this could be the genetic or environmental factors . or certain viruses

    • Symptoms:
      • Varied, unpredictable, include visual problems, limb weakness, muscle spasms, loss of sensation, speech difficulty, tremors, dizziness, bladder control issues, depression.
    • Treatment:
      • No cure; drugs reduce symptoms, lifestyle adjustments to cope with daily activities.
        Placing a bar of soap into old stocking, so that it can be easy to grab when washing

Unit 4: Injuries to the Brain and Spine

  • 4.1 Brain and Spinal Damage:

    • Serious due to limited healing of nervous tissue within the CNS.
      • Effects are often permanent.
    • Brain Injury:
      • Destruction of brain cells, affecting movement, memory, speech.
      • Can result in mental handicap or coma.
    • Spinal Damage:
      • Paralysis (loss of movement) and sensation below the break.
    • Causes:
      • Motor vehicle accidents, acts of violence, sports injuries, falls, violent shaking in young children, spinal cord compression.
    • Most common in young males (15-24).
      *Use protective gear: such as (seat belts and helmet

    Figure 6.20 This person has suspected spinal injury and her spinal column has been immobiliized.

  • 4.2 Possibility of Repairing Injuries:

    • Immediate treatment:
      • Do not move the injured person to avoid further damage (immobilize head/neck).
    • Medical treatment can make a difference between recovering, permanent disability, or death.
      Anti-inflammatory drugs help reduce nerve-cell damage.
      Ongoing physical rehabilitation, occupational and speach tharopy may allow injuries to regain some filling and function\

  • 4.3 Stem Cell Research:

    • Stem cells are capable of dividing and differentiating into almost any of the cell types in the human body.
      • Researchers investigate stem cells to treat spinal cord injuries.
        Stem cells could form new neurons, replacing the damaged ones.
        Activity 6: Review diseases and injuries of the nervous system.

Unit 5: Effects of Certain Drugs on the Central Nervous System

  • Addictive drugs affect the formation of neurons in the brain.
    Serotonin has is known for sleeping, aggression, eating. depressio and body temperature
    Dopamine is important in regulating behavior and motor activity
    *Harmful effect
  • Dagga: Loss of memory, emotional problems with sterlity. Can lead to lung ancer
    *Heroin: An addict' main aim finding and drugs.
  • Ectasy increases risk of mental health problems
    There are many organizations to help people, such as Masalela (MAPSA)
  • Activity 7: Identify why celebrities may battle with

Unit 6: Receptors

  • Receptors detect changes in stimuli (internal and external environments).

  • 6.1 Detection of Stimuli:

    • Interoceptors: Stimulated by internal stimuli (hunger, thirst, pain, etc.).
      stimulate by stimuli in the external environments are
      light
      sounds
      chemical such as taste
      and mechanical touch.

  • 6.2 Human Eye:

    • Converts light into nerve impulses for brain interpretation.
      • Bone, eyelids, eyelashes protect eyes from mechanical injury.

The structure of the eye

  • sclera (maintains the shape of an eyeball
  • cornea( allows light to pass into the eye
    Retins, light to nerve conversion
    Lens which allows us to see behind the pupil.
  • the accommodation. which makes the lens shift its shape
  • pupil refelex mechanism to control the light entering
    Figure 6.24 How the human eye sees: -binocular view enables three dimentional view
    Accommodation 6
    due to
    eye vision such as: short, long, clouding due to uneven curves.
    Astigmatism: When a person has blurred visual defects due to uneven curves. This can be treated with eyeglasses. cataracts. When a person can no longer see. This can be surgically corrected.
    Formal Assessment: Practical task-Activity 9
    Activity 10: Interpret data on visual defects