Introduction to Mental Illness and Degenerative Diseases

In our study of Coordination and Response, we have seen how the nervous system acts like a high-speed communication network. But what happens when this system encounters problems? In this chapter, we explore two types of conditions that affect the brain: mental illnesses and degenerative diseases.

Understanding these conditions is not just about biology; it is about understanding the challenges many people face every day. While mental illnesses often relate to how the brain processes information and emotions, degenerative diseases involve the physical breakdown of the brain's "wiring" over time.


1. Mental Illnesses

A mental illness is a condition that affects a person's thinking, feeling, or mood. These conditions can impact how someone relates to others and functions in daily life. For your Edexcel exam, you need to know about Schizophrenia and Depression.

Schizophrenia

Schizophrenia is a long-term mental health condition that causes a range of different psychological symptoms. It is often misunderstood as "split personality," but in biology, we focus on it as a disruption in brain coordination.

  • Causes: It is believed to be caused by a combination of genetic factors (it can run in families) and imbalances in brain chemicals called neurotransmitters, particularly dopamine.
  • Symptoms:
    — Hallucinations: Hearing or seeing things that do not exist (e.g., hearing voices).
    — Delusions: Holding strong beliefs that are not true.
    — Disorganised thinking: Difficulty keeping track of thoughts or conversations.
  • Treatments: Usually a combination of antipsychotic medication (to balance brain chemicals) and Cognitive Behavioural Therapy (CBT).

Depression

Depression is more than just feeling "unhappy" for a few days. It is a persistent feeling of sadness and loss of interest that lasts for weeks or months.

  • Causes: Often linked to low levels of the neurotransmitter serotonin. It can be triggered by stressful life events, but also has a genetic component.
  • Symptoms:
    — Persistent low mood or sadness.
    — Feeling tired and having no energy (lethargy).
    — Loss of interest in activities once enjoyed.
    — Changes in sleep patterns (too much or too little).
  • Treatments: Antidepressant medications (which help increase serotonin levels) and talking therapies like counselling or CBT.

Quick Takeaway: Mental illnesses like schizophrenia and depression are biological conditions often linked to chemical imbalances (neurotransmitters) in the brain.


2. Degenerative Diseases

A degenerative disease is a condition in which the function or structure of tissues or organs changes for the worse over time. In the context of the nervous system, this usually means neurones (nerve cells) are being damaged or dying.

Alzheimer’s Disease

This is the most common cause of dementia. It involves the physical death of neurones in the brain.

  • Causes: A build-up of abnormal proteins (called plaques and tangles) in the brain. These proteins interfere with how neurones communicate and eventually cause them to die.
  • Symptoms:
    — Short-term memory loss (e.g., forgetting recent conversations).
    — Confusion and disorientation.
    — Difficulty performing familiar tasks.
  • Treatments: There is currently no cure. Treatments focus on medication that can temporarily improve symptoms or slow down the progression for a short time.

Vascular Dementia

While Alzheimer's is caused by protein build-up, Vascular Dementia is caused by reduced blood flow to the brain.

  • Causes: Damage to the blood vessels in the brain, often due to small "mini-strokes" or high blood pressure. If neurones don't get enough oxygen and glucose from the blood, they die.
  • Symptoms: Problems with concentration, planning, and "slowing" of thought processes. Memory loss may occur later than in Alzheimer's.
  • Treatments: Focusing on the underlying cause, such as drugs to lower blood pressure or statins to reduce cholesterol, to prevent further damage.

Parkinson’s Disease

Parkinson’s specifically affects the part of the brain responsible for coordinating movement.

  • Causes: The loss of specific neurones that produce a neurotransmitter called dopamine. Without enough dopamine, the brain cannot send clear signals to the muscles.
  • Symptoms:
    — Tremors: Involuntary shaking, usually starting in the hand or arm.
    — Stiffness: Muscles feel tight and difficult to move.
    — Bradykinesia: This is a fancy word for "slowness of movement."
  • Treatments: Medication (such as L-dopa) that the brain can turn back into dopamine, and physiotherapy to help with movement and balance.

Quick Takeaway: Degenerative diseases are progressive, meaning they get worse over time as more neurones are lost. Alzheimer’s involves protein build-up, Vascular Dementia involves blood flow, and Parkinson's involves dopamine loss.


Summary Table: Key Differences

Use this table to help you distinguish between the conditions for your revision.

Schizophrenia: Chemical imbalance (Dopamine); Hallucinations/Delusions; Antipsychotics.
Depression: Chemical imbalance (Serotonin); Low mood/Energy; Antidepressants.
Alzheimer’s: Protein plaques; Memory loss; No cure, some meds.
Vascular Dementia: Blood flow issues; Planning/Concentration; Blood pressure meds.
Parkinson’s: Dopamine neurone loss; Tremors/Stiffness; Dopamine-replacing meds.


Common Mistakes to Avoid

  • Confusing the neurotransmitters: Remember, Depression is mainly serotonin, while Parkinson’s is the loss of cells that make dopamine.
  • Cure vs. Treatment: Be careful with your language. For degenerative diseases like Alzheimer’s, we talk about "managing" or "slowing" symptoms, not "curing" them.
  • Dementia vs. Alzheimer’s: Remember that Dementia is a general term for a decline in mental ability, and Alzheimer's is a specific disease that causes it.

Memory Aid: The "Three P's" of Parkinson's

To remember the symptoms of Parkinson's disease, think of P-S-T:

1. Posture/Physical slowness (Bradykinesia)

2. Stiffness (Rigidity)

3. Tremors (Shaking)


Note: This chapter connects closely to the "Nervous system" chapter. If you are struggling to understand how neurotransmitters work, go back and review the section on Synapses!