Body Control and Response

Body Control and Response

• Organisms use feedback mechanisms coordinated by the nervous and endocrine systems.
• These mechanisms help maintain homeostasis enabling reproduction and survival.
• The nervous system coordinates and regulates feedback mechanisms to maintain homeostasis.

Module Overview

• The human body's two main regulatory systems are the nervous and endocrine systems.
• These systems function and interact to maintain homeostasis, ensuring proper body function.

Introduction to Body Regulation

• Homeostasis maintains a stable internal environment despite external changes.
• It keeps vital conditions (body temperature, blood pressure, pH, glucose) within a narrow range.
• Both the nervous and endocrine systems regulate homeostasis by sending signals throughout the body.

Control Systems

• Nervous System:
  • Uses electrical signals for rapid communication throughout the body.
  • Enables quick responses like reflexes and immediate heart rate changes.
  • The brain and spinal cord process information to maintain balance.
• Endocrine System:
  • Regulates body functions slowly by releasing hormones into the bloodstream.
  • Hormones control growth, metabolism, reproduction, and long-term stress responses.
  • The endocrine system ensures stability over time by adjusting processes like blood sugar and energy levels.

Nervous vs. Endocrine Systems

The Nervous System

• Neurons (nerve cells) help the body detect stimuli and respond.
• Two major parts: Central Nervous System (CNS) and Peripheral Nervous System (PNS).
• CNS includes the brain and spinal cord, processing information.
• PNS consists of nerves outside the CNS that connect it to the rest of the body.
• The nervous system allows interaction with stimuli and facilitates biological processes.
• Senses send information to the brain, triggering reactions to stimuli.
• The brain has about 100 billion neurons with a cell body and extensions.
• Shorter dendrites receive signals, passing them to the cell body.
• Signals then pass through the axon.

Neuron Basics

• The neuron is the basic functional cell of the nervous system.
• It transmits impulses up to 250 mph.

Neuron Parts

• Dendrite - receives stimuli and carries impulses to the cell body
• Cell Body - contains the nucleus and cytoplasm
• Axon - fiber carrying impulses away from the cell body
• Schwann Cells - produce myelin or fat layers in the Peripheral Nervous System
• Myelin Sheath - dense lipid layer insulating the axon and makes the axon look grey.
• Node of Ranvier - gaps in the myelin sheath
• Impulses travel from dendrites to the cell body and then along the axon

Types of Neurons

• Sensory neurons bring messages to the CNS
• Motor neurons carry messages from the CNS
• Interneurons exist between sensory and motor neurons in the CNS

Impulses

• A stimulus is an environmental change strong enough to start a response.
• Excitability is a neuron's ability to respond and convert stimuli into nerve impulses
• The "all or nothing" rule states that a stimulus is either strong enough to cause an impulse or nothing happens.
• Impulses maintain strength along the neuron and self-propagate in one direction from dendrite to cell body to axon.
• Nerve impulses cause ion movement across the cell membrane.

Synapse

• The synapse is a space between an axon of one neuron and the dendrite of another, without physical contact.
• It's a junction using neurotransmitters to start impulses in the next neuron or effector (muscle/gland).
• Synapses ensure one-way impulse transmission.

Neurotransmitters

• These are chemicals that facilitate the start of impulses in the second neuron across the junction

Central vs. Peripheral Nervous Systems

• The CNS contains the brain and spinal cord, protected by the skull and vertebral column.
• The PNS includes all other nerves in the body.

Nervous System Functions

• Somatic/Voluntary: enables body movement
• Sensory: detects internal and external stimuli
• Autonomic/Involuntary: maintains essential body functions without conscious awareness
• Cognitive: enables thinking and remembering

Central Nervous System

• Parts of the Brain:
  • Brain Stem: Includes the medulla, pons, and midbrain
  • Diencephalon: Thalamus and hypothalamus
  • Cerebellum
  • Cerebrum
• Spinal Cord

Meninges

• Meninges cushion, protect, and nourish the brain/spinal cord.
  • Dura mater: the tough, outer layer
  • Arachnoid mater: the middle layer
  • Pia mater: the transparent, inner layer covering the brain's crevices

Regions of the Brain

• Cerebellum: Coordinates movement and motor learning
• Cerebrum: Handles conscious activities like perception, emotion, thinking, and planning
• Thalamus: Acts as a brain switchboard, filtering and relaying information
• Medulla: Controls vital reflexes like heartbeat and respiration
• Brainstem: Consists of the medulla, pons, and midbrain, relaying information from the spine to the upper brain
• Hypothalamus: Regulates internal organ activities, monitors the autonomic nervous system, controls the pituitary gland and its hormones as well as regulating sleep and appetite.

Lobes of the Cerebrum

• Frontal: involved in movement, planning, and coordinating behavior
• Parietal: involved in sensory processing, attention, and language
• Temporal: involved in auditory perception, speech, and visual perceptions
• Occipital: visual center for processing visual information

Peripheral Nervous System

• Cranial Nerves: 12 pairs attached to the brain's underside.
• Spinal Nerves: 31 pairs attached to the spinal cord.

Somatic Nervous System

• Relays information voluntarily from skin, sense organs, & skeletal muscles to the CNS.
• Brings responses back to skeletal muscles for voluntary action

Autonomic Nervous System

• The Autonomic Nervous System regulates involuntary bodily responses.
• It relays information to internal organs.
• It consists of two divisions:
  • Sympathetic: activated during stress (emergency response, fight or flight)
  • Parasympathetic: active during normal conditions. (everyday conditions)

Major Sense Organs

• Major sense organs are needed for sensation and perception.
• They consist of: vision (via eyes), hearing (via ears), taste (via taste receptors), smell (via the olfactory system), and the skin for sensing hot, cold, pressure, and pain

The Endocrine System

• Glands release hormones circulating to target tissues/organs for regulatory changes, which is slower but has longer-term effects than the nervous system
• Hormones coordinate bodily functions by carrying messages through blood to various tissues and organs.

Endocrine Functions

• Growth, metabolism, and tissue maturation
• Ionic regulation (blood ion concentration)
• Water balance (solute concentration control)
• Heart rate and blood pressure regulation
• Blood glucose and immune system regulation
• Reproductive function control
• Uterine contractions and milk release

Endocrine Glands and Their Hormones

1. Hypothalamus

• Location: Brain, above the pituitary gland
• Function: Connects the nervous system to the endocrine system, controlling the pituitary gland.
• Hormones Released:
  • Releasing Hormones (RHs):
  • Thyrotropin-releasing hormone (TRH) stimulates thyroid hormone release
  • Corticotropin-releasing hormone (CRH) stimulates cortisol production
  • Gonadotropin-releasing hormone (GnRH) stimulates reproductive hormones
  • Growth hormone-releasing hormone (GHRH) stimulates growth hormone
  • Inhibiting Hormones (IHs):
    • Growth hormone-inhibiting hormone (GHIH) (somatostatin) stops growth hormone release
    • Dopamine (Prolactin-inhibiting hormone, PIH) prevents prolactin secretion
  • Oxytocin controls labor contractions and bonding (stored in the posterior pituitary)
  • Antidiuretic Hormone (ADH, Vasopressin) regulates water balance (stored in the posterior pituitary).

2. Pituitary Gland

• Location: Below the hypothalamus in the brain
• Function: Controls other endocrine glands, regulates growth, metabolism, and reproduction.
• Hormones Released:
  • Anterior Pituitary:
    • Growth Hormone (GH) stimulates body growth and metabolism
    • Thyroid-Stimulating Hormone (TSH) signals the thyroid to release thyroid hormones
    • Adrenocorticotropic Hormone (ACTH) stimulates adrenal glands to produce cortisol
    • Follicle-Stimulating Hormone (FSH) regulates egg/sperm production
    • Luteinizing Hormone (LH) triggers ovulation/testosterone
    • Prolactin (PRL) stimulates breast milk production
  • Posterior Pituitary (stores and releases hormones from the Hypothalamus):
    • Oxytocin controls uterine contractions and bonding
    • Antidiuretic Hormone (ADH, Vasopressin) helps retain water and regulate blood pressure

3. Pineal Gland

• Location: Deep in the brain, between hemispheres
• Function: Regulates sleep-wake cycles
• Hormone Released:
  • Melatonin - Regulates sleep patterns based on light exposure

4. Thyroid Gland

• Location: Front of neck, around the trachea
• Function: Controls metabolism, energy levels, and body temperature
• Hormones Released:
  • Thyroxine (T4) & Triiodothyronine (T3)regulate metabolism, heart rate, and digestion

5. Parathyroid Glands

• Location: Four small glands behind the thyroid gland
• Function: Controls calcium levels in the blood
• Hormone Released:
  • Parathyroid Hormone (PTH) increases calcium levels by releasing calcium from bones and enhancing calcium absorption in the intestines

6. Thymus Gland

• Location: Upper chest, behind the sternum
• Function: Develops the immune system
• Hormone Released: -Thymosin stimulates the development of T-cells (immune system cells)

7. Adrenal Glands (The Stress Regulators)

• Location: On top of each kidney
• Function: Controls response to stress, metabolism, and blood pressure.
• Hormones Released:
  • Adrenal Medulla (Inner Layer) Short-Term Stress Response
    • Epinephrine (Adrenaline) increases heart rate and energy, a fight-or-flight response
    • Norepinephrine (Noradrenaline) helps control blood pressure and alertness
  • Adrenal Cortex (Outer Layer) Long-Term Stress Response
    • Cortisol regulates metabolism, immune response, and stress adaptation
    • Aldosterone maintains blood pressure by controlling salt and water balance
    • Androgens are precursors to sex hormones, affecting development in both sexes

8. Pancreas

• Location: Behind the stomach
• Function: Regulates blood sugar
• Hormones Released:
  • Insulin lowers blood sugar
  • Glucagon raises blood sugar
  • Somatostatin regulates insulin and glucagon

9. Gonads

• Ovaries (Females)
  • Location: Lower abdomen
  • Function: Controls female development, menstrual cycle, and pregnancy
  • Hormones Released:
    • Estrogen regulates menstrual cycles, female development and pregnancy
    • Progesterone prepares the uterus for pregnancy and regulates the menstrual cycle
• Testes (Males)
  • Location: Scrotum, outside the body
  • Function: Controls male development, sperm production, and libido
  • Hormone Released:
    • Testosterone develops male secondary sex characteristics and supports sperm production

10. Kidneys as an Endocrine Gland

• Location: Lower back, on either side of the spine
• Function: Filters blood, regulates water/electrolyte balance, produces hormones for blood pressure, red blood cell production, and calcium balance
• Hormones Released:
  • Erythropoietin (EPO) stimulates red blood cell production
  • Renin helps regulate blood pressure
  • Calcitriol (Active Vitamin D3) helps absorb calcium
  • Prostaglandins controls blood flow and inflammation

Communication Between Nervous and Endocrine Systems

• The nervous and endocrine systems work together to regulate body responses.
• The nervous system detects changes and signals the endocrine system.
• This interaction maintains balance and ensures survival.

Bodily Processes

• Stress Response (Fight-or-Flight):
  • Sensory neurons detect danger and send signals to the brain
  • The sympathetic nervous system activates adrenal glands
  • Adrenal glands release adrenaline, increasing heart rate, breathing, muscle strength, and alertness
• Blood Sugar Regulation:
  • The brain detects high blood sugar and signals the pancreas to take action
  • The pancreas releases insulin to lower blood sugar
  • If blood sugar drops too low, the pancreas releases glucagon to signal the liver to release stored glucose
• Growth and Development (Puberty):
  • The hypothalamus releases gonadotropin-releasing hormone (GnRH)
  • The pituitary gland releases FSH and LH, stimulating the gonads
  • The gonads release sex hormones, leading to physical changes
• Temperature Regulation:
  • The hypothalamus detects cold and signals the thyroid
  • The thyroid releases thyroxine (T4), increasing metabolism to generate heat
  • Adrenal glands release adrenaline to boost metabolism/shivering
• Sleep Regulation:
  • The eyes detect darkness and send signals to the hypothalamus
  • The pineal gland releases melatonin
  • The nervous system reduces body activity