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Questions and Answers
Which type of geotropism refers to growth away from gravity?
Which type of geotropism refers to growth away from gravity?
Roots exhibit negative phototropism by moving away from light.
Roots exhibit negative phototropism by moving away from light.
True
What is the term for the response of plant parts to chemical stimuli?
What is the term for the response of plant parts to chemical stimuli?
Chemotropism
The movement of plant parts in response to touch is called __________.
The movement of plant parts in response to touch is called __________.
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Match the following tropisms with their definitions:
Match the following tropisms with their definitions:
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What is the primary function of the nervous system?
What is the primary function of the nervous system?
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Dendrites are responsible for sending signals away from the neuron.
Dendrites are responsible for sending signals away from the neuron.
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What is the role of the axon in a neuron?
What is the role of the axon in a neuron?
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The _____ is the specialized cell responsible for the transmission of nerve impulses.
The _____ is the specialized cell responsible for the transmission of nerve impulses.
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Match the parts of a neuron with their functions:
Match the parts of a neuron with their functions:
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Study Notes
Plant Responses
- Geotropism: Growth in response to gravity. Roots exhibit positive geotropism (grow towards gravity), while shoots display negative geotropism (grow away from gravity).
- Phototropism: Growth in response to light. Stems exhibit positive phototropism (grow towards light), while roots demonstrate negative phototropism (grow away from light).
- Hydrotropism: Growth in response to water or moisture. Roots exhibit positive hydrotropism (grow towards water).
- Chemotropism: Growth in response to chemical stimuli. An example is the growth of the pollen tube towards the ovule, which is a positive chemotropism.
- Thigmotropism: Growth in response to touch. Tendrils wrapping around a support is an example of positive thigmotropism.
The Endocrine System
- Exocrine glands: Release secretions through ducts onto an epithelial surface.
- Endocrine glands: Ductless glands that release hormones directly into the bloodstream. Examples include the pituitary, thyroid, adrenal, pineal, pancreas, ovary (female), and testis (male).
Nervous System
- The nervous system is the body's control center, made up of nervous tissue.
- Neurons: Basic structural and functional units of the nervous system. Responsible for transmitting nerve impulses.
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Neuron structure:
- Cell body (soma): Contains the nucleus and other organelles. Maintains the cell's functions.
- Dendrites: Branching structures that receive signals from other neurons and transmit them towards the cell body.
- Axon: Long, thread-like structure that carries impulses away from the cell body. Ends in axon terminals, which transmit signals to other neurons, muscles, or glands.
- Myelin sheath: Insulates the axon and speeds up nerve impulse transmission.
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Working of a neuron:
- Stimulus received: The neuron receives a stimulus that initiates an electrical signal called an action potential.
- Impulse generation: The action potential is generated at the cell body and travels along the axon.
- Impulse propagation: The nerve impulse moves down the axon towards the axon terminals.
- Synapse transmission: Neurotransmitters are released at the synapse to transmit the signal to the next neuron or target cell.
- Response: The signal leads to a response, such as muscle contraction or hormone release.
CNS (Central Nervous System)
- Consists of the brain and spinal cord.
- The brain controls bodily functions, while the spinal cord relays signals between the brain and the peripheral nervous system.
Human Brain
- Serves as the central coordination hub of the body, enabling thinking and action.
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Regions of the Brain:
- Forebrain: Composed of the cerebrum.
- Midbrain: Composed of the hypothalamus.
- Hindbrain: Composed of the cerebellum, pons, and medulla oblongata.
Forebrain
- The largest brain region responsible for receiving sensory impulses.
- Cerebrum: The uppermost structure of the brain, responsible for thinking, reasoning, speech, information processing, voluntary motor actions, sensory perceptions, learning, and memory.
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Lobes:
- Frontal: Controls voluntary muscle movements, memory, and speech.
- Parietal: Responsible for touch and taste.
- Temporal: Responsible for smell and hearing.
- Occipital: Responsible for vision.
Midbrain
- Contains the hypothalamus.
- Hypothalamus: Located at the base of the cerebrum. Controls eating, drinking, sleep, and wake cycles.
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Pituitary gland: Pea-sized gland situated at the base of the brain. Functions as the master gland, overseeing the secretions of all other endocrine glands. Produces Growth Hormone (GH), LH, and FSH.
- Insufficient GH secretion: Results in dwarfism.
- Excessive GH secretion: Leads to gigantism in children and acromegaly in adults.
Thyroid Gland
- Butterfly-shaped gland in the throat.
- Secretes the hormone thyroxine, which regulates body metabolism.
- Requires iodine for thyroxine synthesis.
- Iodine deficiency: Results in under-secretion of thyroxine and goiter.
Pancreas
- Leaf-like gland located behind the stomach.
- Functions as both an endocrine and exocrine gland.
- Endocrine function: Produces insulin and glucagon, which act antagonistically to regulate blood sugar levels.
- Exocrine function: Secretes enzymes to break down proteins, lipids, carbohydrates, and nucleic acids in food.
- Insufficient insulin production: Results in diabetes.
Adrenal Gland
- Located in pairs above each kidney.
- Size decreases with age.
- Secretes adrenaline, which facilitates the flight and fight response.
- Also secretes noradrenaline.
Gonads
- Gamete-producing organs.
- Testes (male): Produce androgen (testosterone and other male hormones).
- Ovaries (female): Produce estrogen and progesterone (female hormones).
- Androgen and estrogen: Contribute to gamete production and influence the sexual characteristics of males and females, respectively.
- Progesterone: Functions as the pregnancy hormone.
Reflex Arc
- A rapid, involuntary response to a stimulus.
- Components:
- Stimulus: The input signal that initiates the reflex.
- Receptor: Detects the stimulus.
- Sensory neuron: Transmits the signal to the spinal cord.
- Spinal cord: Processes the signal and sends a response back to the effector.
- Motor neuron: Relays the response from the spinal cord to the effector.
- Effector: The muscle or gland that carries out the response.
- Response: The output action that results from the reflex.
- Example: The blinking reflex.
- Stimulus: Bright light.
- Receptor: Photoreceptors in the eye.
- Sensory neuron: Transmits the signal to the spinal cord.
- Spinal cord: Processes the signal.
- Motor neuron: Relays the response to the muscles in the eyelid.
- Effector: Muscles of the eyelid.
- Response: Blinking.
Muscle Cells
- Contain special proteins that change their shape and arrangement in response to electrical impulses, causing the muscle to shorten or contract.
Hormones
- Chemical substances secreted in trace amounts by specialized tissue called endocrine glands.
- Example: Thyroxin hormone, produced by the thyroid gland, regulates metabolism of carbohydrates, fats, and proteins.
Auxin
- Hormone synthesized at the shoot tips.
- Helps plants respond to light by stimulating cell elongation on the shady side of the shoot, causing the plant to bend towards the light.
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Description
Test your knowledge on plant responses such as geotropism, phototropism, and hydrotropism, along with the features of the endocrine system. This quiz covers various growth reactions in plants and the roles of exocrine and endocrine glands. Perfect for biology students looking to reinforce their understanding of these vital concepts.
