The Nervous system + Endocrine system Flashcards
Overview of the Nervous System and the Endocrine System
Nervous System: A fast, complex communication network within the body that uses electrical impulses to send signals to and from the brain, spinal cord, and peripheral organs.
**Divided into two main systems: **
* Central Nervous System (CNS)
* Peripheral Nervous System (PNS).
Endocrine System: A slower communication system that uses hormones released by glands to regulate bodily functions over longer periods.
Works closely with the nervous system to maintain homeostasis and respond to stress.
Structure of the Nervous System
Central Nervous System (CNS):
* Brain: The control centre, responsible for complex functions like cognition, emotion, and movement.
* Spinal Cord: The communication link between the brain and the body, involved in reflex actions and transmitting messages.
Peripheral Nervous System (PNS):Connects the CNS to the rest of the body.
* Sensory Nervous System (SNS): Controls voluntary movement and transmits sensory information to the CNS.
* Motor Nervous System (ANS): Regulates involuntary functions such as heart rate, digestion, and respiratory rate. Subdivided into the sympathetic and parasympathetic nervous systems.
Autonomic Nervous System (ANS) Subdivisions
Sympathetic Nervous System:Prepares the body for “fight or flight” during stressful situations.
Key Functions: Increases heart rate, dilates pupils, inhibits digestion, and stimulates adrenaline release.
Parasympathetic Nervous System: Responsible for “rest and digest,” calming the body after the threat has passed.
o Key Functions: Slows heart rate, stimulates digestion, conserves energy, and reduces breathing rate.
Key Differences:
* Sympathetic: Arouses the body, energising it for action.
* Parasympathetic: Calms the body and restores normal function.
The Reflex Arc
* Definition: A fast, automatic response to a stimulus that bypasses the brain for quicker reaction times.
o Involves sensory neurons, relay neurons, and motor neurons.
* How it Works:
1. Sensory neurons detect a stimulus (e.g., touching something hot) and send a signal to the spinal cord.
2. Relay neurons pass the signal to motor neurons.
3. Motor neurons send impulses to muscles, causing a reflexive action (e.g., withdrawing your hand).
The Endocrine System
* Definition: A series of glands that produce and secrete hormones directly into the bloodstream.
* Hormones: Chemical messengers that regulate physiological processes such as growth, metabolism, and reproduction.
o Example: Adrenaline is secreted by the adrenal glands to prepare the body for a fight-or-flight response.
* Key Glands:
o Hypothalamus: Links the nervous system to the endocrine system via the pituitary gland.
o Pituitary Gland: The “master gland” that regulates other endocrine glands.
o Adrenal Glands: Produce adrenaline and cortisol during stress.
The Fight or Flight Response
* Definition: The body’s rapid, automatic response to perceived threats, initiated by the sympathetic nervous system and the release of adrenaline.
* Process:
1. Perception of a Threat: Detected by the amygdala, signals are sent to the hypothalamus.
2. Activation of the Sympathetic Nervous System: Triggers the adrenal medulla to release adrenaline into the bloodstream.
3. Physiological Changes: Increased heart rate, blood pressure, and energy availability (glucose release). Pupils dilate, digestion slows.
4. After the Threat: Parasympathetic system calms the body by lowering heart rate and promoting digestion.
The Hypothalamic-Pituitary-Adrenal (HPA) Axis
* Definition: The body’s slower, long-term stress response system.
How it Works:
1. The hypothalamus releases corticotropin-releasing hormone (CRH), which signals the pituitary gland.
2. The pituitary gland releases adrenocorticotropic hormone (ACTH) into the bloodstream.
3. The adrenal cortex responds by releasing cortisol, which maintains energy levels and suppresses non-essential functions (like digestion and immune responses).
Cortisol Effects: Provides energy by increasing blood sugar, but prolonged exposure can weaken the immune system and impair cognitive function.
Evaluation of the Fight or Flight Response
* Strengths:
1. Adaptive Function: The fight-or-flight response is essential for survival, helping organisms respond to threats rapidly.
2. Physiological Support: Clear evidence of adrenaline’s role in preparing the body for physical action (increased heart rate, blood flow).
* Limitations:
1. Modern-Day Stress: Most modern stressors (e.g., exams, work) do not require physical action, leading to negative health effects from chronic activation of this system (e.g., cardiovascular disease).
2. Tend-and-Befriend Response: Taylor et al. (2000) suggest women may show a different response to stress, often seeking social support rather than engaging in fight or flight, likely due to evolutionary pressures of protecting offspring.
Research Evidence for the Role of the Endocrine System
* Selye’s General Adaptation Syndrome (1956):
* Identified the three stages of the body’s stress response: alarm, resistance, and exhaustion.
* Found that chronic stress leads to depletion of energy resources, increasing the risk of stress-related illnesses (e.g., heart disease).
* Evaluation: Demonstrates the importance of the HPA axis in prolonged stress responses, but the model is based on animal research, which limits its application to human stress responses.
* Dabbs et al. (1995):
* Findings: Higher levels of testosterone (an endocrine hormone) were linked to aggressive behaviour in male prisoners, supporting the influence of hormones on behaviour.
* Evaluation: Provides evidence for hormonal effects on behaviour but correlational studies cannot establish cause and effect.
Key Exam Points for the Nervous and Endocrine Systems
Definitions: Clearly differentiate between the nervous system (fast, electrical signals) and the endocrine system (slow, hormonal signals).
Key Structures: Ensure you know the roles of the CNS, PNS, ANS (sympathetic/parasympathetic divisions), and glands like the adrenal and pituitary.
**Fight or Flight Response: **Be able to explain how the sympathetic nervous system and adrenal glands initiate the response, and how the parasympathetic system restores homeostasis.
HPA Axis: Discuss the role of cortisol and its long-term effects on stress management.
Evaluation: Include strengths (adaptive value, research evidence) and limitations (modern stressors, alternative responses like tend-and-befriend).
