when a person looks at a bright light, tiny muscles in the eye contract so less light can enter the eye. which are most likely the characteristics of this muscle? select three options. nonstriated involuntary voluntary striated attached to skull attached to the eyeball

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Science Test 2 Section 4 Flashcards

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Science Test 2 Section 4

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The hair on Jamal's arms is standing straight up.

What most likely explains why his hair is behaving this way?

He is in a cold area.

He is sweating.

He is in danger of bacteria.

He is receiving information for touch.

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He is in a cold area.

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Which is the biggest muscle in the human body?

gluteus maximus gluteus minimus sartorius heart

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gluteus maximus

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Terms in this set (16)

The hair on Jamal's arms is standing straight up.

What most likely explains why his hair is behaving this way?

He is in a cold area.

He is sweating.

He is in danger of bacteria.

He is receiving information for touch.

He is in a cold area.

Which is the biggest muscle in the human body?

gluteus maximus gluteus minimus sartorius heart gluteus maximus

What do the stapedius and gluteus maximus have in common?

They move the hips and thighs.

They are attached to bones.

They are the largest muscles.

They are the smallest muscles.

They are attached to bones.

Henry touched a hot plate and immediately moved his finger away from it.

Which best explains the integumentary system's role in this reaction?

Oil in the skin sensed the temperature difference.

Nerve endings in the skin responded to the heat.

Some hairs stood up when the fingers touched the plate.

His nails absorbed heat and moved his finger away from the plate.

Nerve endings in the skin responded to the heat.

When a person looks at a bright light, tiny muscles in the eye contract so less light can enter the eye.

Which are most likely the characteristics of this muscle? Check all that apply.

nonstriated involuntary voluntary striated attached to skull

attached to the eyeball

nonstriated involuntary

attached to the eyeball

Which trait do cardiac and smooth muscle share?

voluntary involuntary nonstriated striated involuntary

Which organs are part of the musculoskeletal system? Check all that apply.

bones hair muscles skin tendons nails bones muscles tendons

Which describes an interaction within the musculoskeletal system?

When a muscle contracts, a bone will move.

When a bone contracts, a muscle will move.

When a tendon contracts, a ligament will move.

When a ligament contracts, a tendon will move.

When a muscle contracts, a bone will move.

Bone marrow can be found in the many hollow spaces in the

type of bone. spongy

To raise an arm upward, the muscle on one side of it contracts.

What happens to the muscle on the opposite side of the arm?

contracts relaxes

both contracts and relaxes

neither contracts nor relaxes

relaxes

Which protects nerve endings at the ends of fingers and toes?

joints hair nails muscle nails

Cardiac muscle causes movement in the .

organ

When Jacob starts running, his legs move faster and his heart rate increases. Which types of muscles are involved in these changes?

Skeletal muscles control his leg movement and smooth muscles control his heart rate.

Skeletal muscles control his leg movement and cardiac muscles control his heart rate.

Smooth muscles control his leg movement and cardiac muscles control his heart rate.

Skeletal muscles control both his leg movement and heart rate.

Skeletal muscles control his leg movement and cardiac muscles control his heart rate.

The hair on Jamal's arms is standing straight up.

What most likely explains why his hair is behaving this way?

He is in a cold area.

He is sweating.

He is in danger of bacteria.

He is receiving information for touch.

...

Which action would be completed by skeletal muscle tissue?

digesting lunch

moving blood through arteries

increasing the heartbeat

kicking a soccer ball

...

The picture represents muscle tissue.

Which type of muscle tissue is pictured?

cardiac skeletal smooth striated ...

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How the eye focuses light — Science Learning Hub

The human eye is a sense organ adapted to allow vision by reacting to light. The cornea and the crystalline lens are both important for the eye to focus light.

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How the eye focuses light

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The human eye is a sense organ adapted to allow vision by reacting to light. The cornea and the crystalline lens are both important for the eye to focus light.

How the eye works

Associate Professor Gordon Sanderson explains how the eye works, focusing on the receptors located in the retina at the back of the eye.

The eye focuses light in a similar way to when you use a magnifying glass to concentrate the Sun’s rays onto a piece of paper. The distance from the magnifying lens to the piece of paper is the focal length.

For the eye, light from distant objects is focused onto the retina at the back of the eye.

The eye is about the size of a table tennis ball, so the focal length needs to be about 2.5 cm.

The cornea does most of the focusing

The eye’s lens system

Using the example of using a magnifying lens to focus light rays onto a piece of paper, ophthalmologist Associate Professor Gordon Sanderson from the University of Otago describes how the lens in the eye functions.

About 70% of the bending of light takes place as it enters the cornea and the aqueous fluid.

This bending is possible because of the curve of the cornea as well as the change in refractive index as light moves from air into the cornea and then into the aqueous fluid between the cornea and the iris. Air has a refractive index of 1.00, and the aqueous fluid behind the cornea has a refractive index of 1.33.

If the change in refractive index was not as great, the light would not bend as much.

This becomes noticeable if you try to look at something when you are under water. Things appear out of focus because the cornea is designed to work with light passing into it from air rather than from water. Wearing swimming goggles under water allows the layer of air to be present.

The crystalline lens and accommodation

Behind the aqueous fluid is the second lens system. It consists of a convex lens that is soft and pliable. The ciliary muscle is a circular ring of muscle that attaches all the way around the lens. This ciliary muscle can change the shape of the crystalline lens by stretching it at the edges. It is attached to the lens by zonules (ligament fibres that can be tight or loose).

When you are looking at a near object, the lens needs to become more rounded at the central surface in order to focus the light rays. This ability to change focus for close-up objects is called accommodation.

Rights: University of Waikato. All Rights Reserved.

Accommodation

The crystalline lens changes shape to accommodate near or far targets. The ability of the eye to change the shape of its lens and its focus is known as accommodation.

Two totally opposite theories for accommodation

There are two main theories for how the lens changes shape.

Helmholtz theory – proposed in 1855. When the ciliary muscle contracts, all zonular tension is reduced. This permits the central lens surface lens to become rounder (increases its focusing power). When the ciliary muscle relaxes, all zonular tension is increased, causing the lens to flatten (decrease in optical power).Schachar mechanism – proposed in 1992. When the ciliary muscle contracts, equatorial zonular tension is increased. This causes the central lens surface to become more steeply rounded (increases central optical power). When the ciliary muscle relaxes, equatorial zonular tension is reduced, causing the central lens surface to flatten (decrease in optical power).

Rights: The University of Waikato Te Whare Wānanga o Waikato

Theories of eye accommodation

The Helmholtz theory of accommodation claims that, as the ciliary muscle contracts, the zonules become loose and the lens becomes rounder. The Schachar theory claims that the zonules become tighter to distort the centre of the lens into a more steeply rounded shape.

The University of Waikato acknowledges the work of Dr R Schachar in creating this diagram.

The Schachar mechanism can be demonstrated using a Mylar balloon (a shiny silver flat balloon that is often used with helium). If you look at your reflected image on the flat side of the balloon, you will notice that it becomes smaller if you pull the edges of the balloon outwards. This is because the centre of the balloon becomes more convex.

Loss of accommodation

As we age, the ability of the ciliary muscle to change the shape of the crystalline lens lessens. For most people, their ability to focus on close-up images decreases, but distance vision is unaffected. This is known as presbyopia and is one reason that older people often need reading glasses.

Presbyopia – the old eye

University of Otago ophthalmologist Associate Professor Gordon Sanderson explains that one of the eye problems associated with ageing is a condition called presbyopia. This involves a deteriorating ability to change the shape of the lens.

Source : www.sciencelearn.org.nz

6.3: Types of Muscle Tissue

Muscle tissue is a soft tissue that makes up most of the tissues in the muscles of the human muscular system. Other tissues in muscles are connective tissues, such as tendons that attach skeletal …

6.3: Types of Muscle Tissue

Last updated May 13, 2020

6.2: Introduction to the Muscular System

6.4: Muscle Contraction

Suzanne Wakim & Mandeep Grewal

Butte College

Work Those Eye Muscles!

Turn your eyes—a tiny movement, considering the conspicuously large and strong external eye muscles that control eyeball movements. These muscles have been called the strongest muscles in the human body relative to the work they do. However, the external eye muscles actually do a surprising amount of work. Eye movements occur almost constantly during waking hours, especially when we are scanning faces or reading. Eye muscles are also exercised nightly during the phase of sleep called rapid eye movement sleep. External eye muscles can move the eyes because they are made mainly of muscle tissue.

Figure 6.3.1 6.3.1 : Eyes

What is Muscle Tissue?

Figure 6.3.2 6.3.2

: Muscle type 1) Skeletal muscle cells are long tubular cells with striations (3) and multiple nuclei (4). The nuclei are embedded in the cell membrane (5) to be just inside the cell. This type of tissue occurs in the muscles that are attached to the skeleton. Skeletal muscles function for the voluntary movements of the body. Muscle type 2) Smooth muscle cells are spindle-shaped (6), and each cell has a single nucleus (7). Unlike skeletal muscle, there are no striations. The smooth muscle acts involuntarily and functions in the movement of substances in the lumens. They are primarily found in blood vessel walls and walls along the digestive tract. Muscle type 3) Cardiac muscle cells branch off from each other, rather than remaining, like the cells in the skeletal and smooth muscle tissues. Because of this, there are junctions between adjacent cells (9). The cells have striations (8), and each cell has a single nucleus (10). This type of tissue occurs in the heart wall, and its primary function is for pumping blood. This is an involuntary action.

Muscle tissue is a soft tissue that makes up most of the tissues in the muscles of the human muscular system. Other tissues in muscles are connective tissues, such as tendons that attach skeletal muscles to bones and sheaths of connective tissues that cover or line muscle tissues. Only muscle tissue per se, however, has cells with the ability to contract.

There are three major types of muscle tissues in the human body: skeletal, smooth, and cardiac muscle tissues. Figure

6.3.2 6.3.2

shows how the three types of muscle tissues appear under a microscope. When you read about each type below, you will learn why the three types appear as they do.

Skeletal Muscle Tissue

Skeletal muscle is muscle tissue attached to bones by tendons, which are bundles of collagen fibers. Whether you are moving your eyes or running a marathon, you are using skeletal muscles. Contractions of skeletal muscles are voluntary or under the conscious control of the central nervous system via the somatic nervous system. Skeletal muscle tissue is the most common type of muscle tissue in the human body. By weight, an average adult male is about 42 percent skeletal muscles, and the average adult female is about 36 percent skeletal muscles. Some of the major skeletal muscles in the human body are labeled in Figures

6.3.3 6.3.3 and Figure 6.3.4 6.3.4 and listed in Table 6.3.1 6.3.1 . Table 6.3.1 6.3.1

: Skeletal muscles. Some muscles are visible from both anterior and posterior views.

rotator cuff (multiple muscles are part of this group)

levator scapulae biceps brachii rhomboids brachialis rotator cuff pronator teres triceps brachii brachioradialis gluteus maximus adductor muscles tibialis posterior tibialis anterior peroneus longus deltoid peroneus brevis pectoralis major trapezius rectus abdominis deltoid

abdominal external oblique

brachioradialis iliopsoas latissimus dorsi quadriceps femoris biceps femoris peroneus longus semitendinosus peroneus bravis semimembranousus gastrocnemius soleus

Figure 6.3.3 6.3.3

: This figure shows major skeletal muscles in the front (anterior) of the body.

Figure 6.3.4 6.3.4

: This figure shows major skeletal muscles in the back (posterior) of the body.

Skeletal Muscle Pairs

To move bones in opposite directions, skeletal muscles often consist of muscle pairs that work in opposition to one another. For example, when the biceps muscle (on the front of the upper arm) contracts, it can cause the elbow joint to flex or bend the arm, as shown in Figure

Source : bio.libretexts.org